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Naively as an outsider, this situation seems like everything worked as intended? On a nominally 2h45m flight, they spent an extra 2 hours in the air, presumabl
by abtinf 1y ago
Naively as an outsider, this situation seems like everything worked as intended?
On a nominally 2h45m flight, they spent an extra 2 hours in the air, presumably doing doing fuel intensive altitude changing maneuvers, and were eventually able to land safely with their reserves almost exhausted.
I’m a little confused by what there is to investigate at all.
How much fuel should they have landed with?
- _9ptr 1y ago30min+
- jacquesm 1y agoYes, I believe this is correct for this model aircraft.
- fabian2k 1y agoMy understanding is that they shouldn't have spent that much time in the air (not intended as a guess for the cause). The margin is there for situations where you can't land earlier, not the margin for scheduling the landing. There is margin for expected potential delays, they were in the other margin that should never be used except in true emergencies.
- abtinf 1y agoOh I think I see; so is the question not “why did they land with so little fuel”, but more like “why did it take so long to decide to redirect to a known-safe airport”?
- fabian2k 1y agoI don't know. As the parent said, I'd be careful with guessing the root cause right now. They should not have been this low even if diverted due to weather.
- jacquesm 1y agoPossibly. Or 'why did your fuel readings deviate from what was actually in the tanks' or 'why did we leave with less fuel than we thought we did' and so on. There are so many variables here speculation is completely pointless. All we know is that something went wrong, that it almost led to a crash and that it involves an airline with a very good record when it comes to things like this. Low fuel happens, but this is (very) exceptional.
- wahnfrieden 1y agoBy asking such a question you understand the need for an investigation
- gregoriol 1y agoFlight from Edinburgh to Manchester is just a bit more than 1 hour, so after trying 2 landings, diverting to Edinburgh (15-20 minutes flight), 1 more landing attempt, well, you get very close to 2 hours.
- gsnedders 1y agoI felt like that seems a little long from EDI to MAN (after all, EDI to LHR is typically a flight time of under an hour!), so: https://globe.adsbexchange.com/?icao=4d2256&lat=54.720&lon=-3.164&zoom=7.7&showTrace=2025-10-03&leg=4 https://globe.adsbexchange.com/?icao=4d2256&lat=54.720&lon=-... is the track of this flight. Went around at EDI at about 19:10Z, landed at about 19:51Z, so about a 41 minute flight.
- gregoriol 1y agoRight, I probably got the information for flight time as seen by a passenger on a ticket, not for a plane already flying. Thanks!
- zerkten 1y agoIf they have to touch and go, how long would it take until they get the plane around for another approach? In fact, you might not get as far as that touch and go and have to go around. You need some margin for all of these eventualities. The likelihood is low that these happen, but they have to be accounted for.
- bluGill 1y agoSure, but the flight was a lot longer than planed. How much extra do we need. They declared an emergency, and thus put themselves at the front of the line. They had 6 more minutes to do that touch and go around if that happened, and since they were already in a low fuel emergency they get priority and so there is enough time to do that if they needed. (edit - as others have noted, 6 minutes with high error bars, so they could have only had 30 seconds left which is not enough) They landed safely, that is what is important. There is great cost to have extra fuel on board, you need enough, but it doesn't look to me like more was needed. Unless an investigation determines that this emergency would happen often on that route - even then it seems like they should have been told to land in France or someplace long before they got to their intended destination to discover landing was impossible.
- jacquesm 1y ago> They had 6 more minutes to do that touch and go around if that happened 6 minutes is way out of the comfort zone. They might not have made it in that case.
- scrumper 1y agoCorrect, article says they landed with 220kg which is around 6 minutes of average fuel burn over an entire flight - bit less at cruise, a hell of a lot more at takeoff/climb. So I don't think 220kg is enough to do a go-around in a 737 (well, a go-around would've been initiated with a bit more than 220kg in the tank - they burned some taxing to the gate - but you get my point.) I've read around 2,300kg for takeoff and climb on a normal flight in a 737-8. A go-around is going to use close to that, it's a full power takeoff but a much shorter climb phase up to whatever procedure is set for the airport and then what ATC tells you. I just flew 172s but even with those little things we were told, your reserve is never to be used. These people came very, very close to a disaster. Fortunately they had as much luck left as they did fuel.
- paulddraper 1y agoAt what point should they investigate? 0 minutes? -1 minutes?
- jacquesm 1y agoAnything less than 60 minutes would be looked at by the airline, anything less than the legally required amount (30 minutes for a jet of this type iirc) will result in a very serious investigation. Note that for slower aircraft (for instance a turbo-prop) the time requirement goes up not down because they may have to spend more time in the air to reach an alternate (or secondary alternate, if things are really bad, like what happened here).
- jenadine 1y agoThey should investigate after the first failed landing, regardless of the amount of fuel in the tank.
- jacquesm 1y agoGo arounds are perfectly normal and are not a 'failed landing', a failed landing is a crash.
- gsnedders 1y agoAs others have said, final fuel reserves are typically at least half an hour, and you shouldn't really be cutting into them. What if their first approach into MAN had led to another go around? With a major storm heading north-easterly across the UK, the planning should have reasonably foreseen that an airport 56 miles east may also be unavailable, and should've further diverted prior to that point. They likely used the majority of their final fuel reserve on the secondary diversion from EDI to MAN, presumably having planned to land at their alternate (EDI) around the time they reached the final fuel reserve. Any CAA report into this, if there is one produced, is going to be interesting, because there's multiple people having made multiple decisions that led to this.
- jacquesm 1y agoJust reaching altitude again to make it to the first and later second alternate are mostly likely the biggest factors in the extra fuel consumption. That's very expensive.
- dTal 1y agoYou get that energy back on descent, no?
- bagels 1y agoSome of it, but much is lost to drag. They do have to limit speed at all times.
- tamcap 1y agoNot really. While you have a large potential energy buildup at a higher altitude, you cannot "bank it" / "save it" on descent. There is no way to store it in batteries or convert it back into fuel. One of the challenges of aeronautics is the efficient disposition of the potential energy without converting it all into kinetic energy (ie speed) so that the landing happens at an optimally low speed - thus giving you a chance to brake and slow down at the end.
- 1y ago
- metalman 1y ago6 min, is empty, 6 min is purely theoretical, 6 min would not clear for ground handling or a test start, or a fuel system check,6 min would not do a go around. will interesting to see if they release info about what the real amount of fuel left is, and an authorative discussion on how much useable flight time was there. did they actualy make the taxi to the terminal?, or run out on the apron?
- jacquesm 1y agoYes. There is another comment above making light of the 6 minutes as if another go-around was still an option, that is a ridiculous take. They were going to bring that plane in and land it no matter what on this last run, otherwise they'd crash for sure. 6 minutes may not even be within the margin of readout.
- scrumper 1y agoI think the article says that someone saw 220kg written on a log - that's about 6 minutes worth at cruise. So yeah, it's zero basically.
- jenadine 1y agoBy your logic you need an infinite amount of fuel. If you define X the amount of fuel you need after you land. And you say that X needs to be enough to make an emergency landing. And we define that the amount of fuel required for an emergency landing should cover the amount required for the landing operation while still having X in the tank when landed. X > X + landing_cost The plane already had made 3 failed attempt before and was redirected to two different airports.
- loverofhumanz 1y ago"I’m a little confused by what there is to investigate at all." You're confused why they should investigate how everyone on that flight came within minutes of dying? Something about the fuel reserves, procedures, or execution was clearly flawed.
- nickff 1y agoFuel depletion is risky, but not that risky; see the Gimli Glider for a case much more dangerous than this, which still worked out amazingly well. Edit: Here is the Wiki on incidents... https://en.wikipedia.org/wiki/Fuel_starvation_and_fuel_exhaustion https://en.wikipedia.org/wiki/Fuel_starvation_and_fuel_exhau...
- loverofhumanz 1y agoDepends largely on the altitude when fuel runs out. If it runs out when they're at 4,000 ft and it's windy, it's probably game over.
- behringer 1y agoAnd what happens if you're not at 40k feet when the fuel runs out?
- 5f3cfa1a 1y agoFuel depletion is _not that risky_ is an interesting take. But hey, it won Chapecoense its first and only Copa Sudamericana, so maybe it isn't that bad after all? https://en.wikipedia.org/wiki/LaMia_Flight_2933 https://en.wikipedia.org/wiki/LaMia_Flight_2933
- kube-system 1y agoI'm not an aviation expert, but generally in safety engineering, safety buffers are not simply calculated as [normal situation] * [safety factor], but [worst case scenario] * [safety factor] If you ever cut into your safety allowance, you've already fucked up. Your expected design criteria should account for all use cases, nominal or worst-case. The safety factor is there for safety, it is never intended to be used.
- jacquesm 1y agoThis is exactly how it is in this case. Any consumption of the fuel reserve would result in an investigation, this is a very extreme case and it may even result in a change in the rules depending on the root cause.
- tonyhart7 1y agoYeah idk people debating about this, if this justifiable then its all gucci and world can learn from such experience
- appreciatorBus 1y agoYes, exactly. The day it's normal to eat into the allowance is the day we start seeing planes falling out of sky for lack of fuel again. The only way to prevent that is to treat 30 min of fuel as seriously as you would 0 minutes.
- abtinf 1y agoThis is really helpful and I think I understand now. The approach is basically “accounting for everything that might go wrong to the best of our experience, including problems arising from the complex interactions between the airplane and supporting ground systems and processes, this is how much fuel you need in the worst case scenario. And now lets add more to give us a cushion, and we will treat consumption of this last reserve as tantamount to a crash.”
- adastra22 1y agoPrecisely.
- constantcrying 1y ago>I’m a little confused by what there is to investigate at all. One of the most important aspects of taking safety seriously is that you do not just investigate things which had an impact, but that you proactively investigate near misses (as was the case here) and even potential incidents. A plane with 6 minutes of fuel left is always a risk to every person on board and potentially others if an emergency landing becomes the only option.
- MadnessASAP 1y agoIndeed that is the definition of a "aviation incident" where there was a risk of injury or damage. If there is actual injury or damage it becomes an "accident". The investigations into incidents aren't usually particularly long or noteworthy and often the corrective action will be to brief X on dangers of Y, or some manner of bulletin distributed to operators.
- Ekaros 1y agoOnly issue I see is that should there have been stricter rules to diverting way earlier. If winds were such as to make landing harder. Would just directly going somewhere else been the correct choice to force.
- jacquesm 1y agoThis is likely one of the questions the investigation will focus on.
- MBCook 1y agoIt also sounds like they went to an alternate airport they probably shouldn’t have bothered with.
- rob74 1y agoWell, if you know you're pretty low on fuel, you are likely to pick an airport where the weather is good, rather than risking three more missed approaches at a closer one where the weather is probably also bad. Of course, Manchester is also a Ryanair base. There are two Ryanair bases closer to Prestwick (Edinburgh and Newcastle), but maybe the weather was bad there too? If the fuel situation was so dire, questions might be asked during the investigation why they didn't pick a closer airport with good weather that wasn't a Ryanair base (if one existed), but ultimately it's the pilots' decision to fly a bit further to an airport they are familiar with, and second guessing them with the benefit of hindsight is probably not a good idea...
- manarth 1y agoThey made two attempts to land at Prestwick, then diverted to Edinburgh (which also had bad weather). After one attempt at Edinburgh, they then diverted to Manchester.
- immibis 1y agoWhether it can be prevented in the future. Should planes fly with even more reserve fuel? It's possible. Or maybe different ways of selecting alternate landing sites? It may even be the answer is "no, everything went as well as it possibly could have, and adding more reserve fuel to every flight would be unacceptably wasteful, so oh well", but at a minimum they'll probably recommend even more fuel on certain flights into risky weather.
- rolph 1y agoideally, enough to divert to another airport, in the off chance something happens, like a pending emergency at point post.
- TheJoeMan 1y agoI think a more insightful answer is how often is it acceptable for the reserves to actually be cut into. If this was happening often, then there’s a likelihood of a future disaster. As it is there is 1 isolated case that still ended with a positive outcome. I think it almost adds support for the current reserve levels to be pretty dialed-in.
- baq 1y agoThe answer is 'never' as the reserves are only added for worse-than-worst case scenario, i.e. in this case something went literally unimaginably (as of then) wrong.
- jacquesm 1y agoOfficially: never. Unofficially, a minute or two would be cause for concern and the regulators would most likely be showing an interest. The airline may have a higher margin than the official one. This is exceptional, they were within the margin of error on readout and the pilots must have known that. It's one thing to know you have half an hour of fuel give-or-take in the tank it is another to know that give-or-take you are running on fumes.
- wat10000 1y agoImagine you're standing on a balcony and discover that the supports are cracked almost all the way through. Do you shrug and say, that's why they have a safety factor, everything worked as intended? Or do you say, holy crap, I nearly died, how did this happen? The purpose of the safety factor is to save you if things go badly wrong. The fact that it did its job doesn't mean things didn't go badly wrong. If you don't address what happened then you no longer have a safety factor.
- lazide 1y agoIf you get shot, but had a bullet proof vest on, and hence didn’t die, technically everything worked as intended. Personally, I’d still want to figure out why I got shot and work on making sure that didn’t happen again. Especially if you basically got shot multiple times (for an analogy in this case).
- appreciatorBus 1y agoDepends if our goal is to have zero aircraft crashes. If the goal is zero, then for any given parameter, you have to define a margin of safety well before crash territory and treat breaching that margin as seriously as if there had been a crash. Similarly planes are kept 5 nautical miles apart horizontally, and if they get closer than that, you guessed it - investigation. Ofc planes could come within inches and everyone could live, but if we normalize flying within inches, the we are also normalizing zero safety margin, turning small minor inevitable human failings into catastrophe death & destruction. As an example, planes communicate with ATC over the radio and are given explicit instructions - turn left 20 degrees, fly heading 140 etc. From time to time these instructions are misunderstood and have to be corrected. At 5nm separation everyone involved has plenty of time to notice that something was missed/garbled/misinterpreted etc and correct. At 1 inch separation, there's no such time. Any mistake is fatal, even though in theory you are safe when separated by 1 inch. TBC an investigation doesn't mean investigating the pilots in order to assign blame, it means investigating the entire aviation system that led up to the breach. The pilot's actions / inaction will certainly be part of that, but the goal is to ask, "How could this have been avoided, and ask how every part of the system that we have some control or influence over might have contributed to the outcome"
- henryfjordan 1y agoWe shouldn't aim for 0 crashes due to low fuel though. How many deaths does carrying around 3x fuel than what you reasonably need contribute to via extra pollution? We should aim for 1 every 10-100 years or something reasonable like that.
- appreciatorBus 1y agoWe should account for deaths from pollution, but if we are going to do that, we should be willing to do that for 99% of aviation fuel that has nothing to do with reserves & safety margins, in addition to fuel used to drive cars. Any regulation short of "carry infinite fuel" will be a trade-off, and entail some risk and anyone involved in setting these knows that. Zero may not be our actual target or even possible, but it is a useful aspiration to ensure that everyone is pulling in the right direction.
- rz2k 1y agoThis reminds of discussions following the Fukushima disaster where one commenter claimed that it wasn't a design flaw, because it was an extraordinary circumstance. I found this appalling, because I do not at all think that was the risk profile that was sold to the public; I think people believed that it was supposed to be designed to safely survive 1000-year earthquakes and the tsunamis that they create. Likewise, I think that the flying public is lead to believe fuel exhaustion is so rare that when airlines are compliant with regulations, no such disasters across all flights across all carriers will occur during your lifetime.
- philipallstar 1y agoI'm sure we can all remember at least one person in any situation who will say something we find memorably awful.
- deleted 1y ago[deleted]
- pornel 1y agoIt's also a communication problem, because labels like "100-year/1000-year event" are easily misunderstood. * they're derived from an estimated probability of the event (independently) happening each year. It doesn't mean that it won't happen for n years. The probability is the same every year. * the probabilities are estimates, trying to predict extreme outliers. Usually from less than 100s of years of data, using sparse records that may have never recorded a single outlier. * years = 1/annual_probability ends up giving large time spans for small probabilities. It means that uncertainty between 0.00001% and 0.00002% looks "off by 500 years". https://practical.engineering/blog/2025/9/16/an-engineers-perspective-on-the-texas-floods https://practical.engineering/blog/2025/9/16/an-engineers-pe...
- kqr 1y agoI find a useful exercise is to have a cheat sheet of historic flood heights in some area, tell someone the first record high, ask them how high they would make the levee and how long they think it would last. Peoples' sense for extremal events is bad.
- LightBug1 1y agoReally? Equally as an outsider - it feels like one "go-around" and you're fucked.
- sgjohnson 1y agoIf you cut into the final reserve, it’s a full-blown emergency requiring a mayday call. This should not happen. So what’s there to investigate? How it was allowed to happen, and how to prevent it from happening again. EDIT: it’s a mayday even earlier than that. It’s a mayday once the pilots know that they WILL land with less than the final reserve.
- jasonwatkinspdx 1y ago> I’m a little confused by what there is to investigate at all. So because the safety margin still worked while down to near vapors we should conclude there's nothing to learn for the future to reduce the risk of similar incidents? That's certainly... a take.
- hshdhdhehd 1y agoI dont know but maybe they should have diverted sooner. Maybe an hour into the flight?
- hayleox 1y agoWell imagine they had to do a go-around on that landing. Go-arounds are extremely normal and might be done for a million reasons; your speed is wrong, your descent rate is wrong, your positioning is wrong, there's bad wind, there's an issue on the ground, etc etc etc. Six minutes of fuel is really not enough to be sure that you can do a go-around. So now, if ANY of those very normal everyday issues occurs, the pilot has to choose between two very bad options: doing a go-around with almost no fuel, or attempting a landing despite the issue. That's just way too close for comfort. Aviation operates on a Swiss cheese model; the idea is that you want many many layers of safety (slices of cheese). Inevitably, every layer will have some holes, but with enough layers, you should still be safe; there won't be a hole that goes all the way through. In this case, they basically got down to their very last slice of cheese; it was just luck that the last layer held.
- hugo1789 1y agoI think he would attempting a landing despite the issue in most cases because running out of fuel during go-around would be worse.
- hinkley 1y agoOne of those YouTube channels where a professional pilot evaluates flying incidents had a similar incident when the pilot started yelling at the tower when they tried to make him go around again. He essentially said he would declare an emergency if he didn’t hear different instructions. I think he had 10-15 minutes when he touched down. One of the things the reserve is for is if the plane immediately in front of you fucks up the runway, you now have to divert to the next airport. You need at least enough fuel to get there and for the tower to shove everyone else out of the way so you can make an emergency landing. There are other reasons someone could abort a landing and have to go around again, besides debris in the runway. And sometimes two of them can happen consecutively. In the case I’m referencing, it was pointed out that p the pilot made things worse by going faster than he was told to fly, using up fuel and also making him too close to a previous plane which forced him to go around the previous time, so it wasn’t all the tower.
- PunchyHamster 1y agoMight not be about fuel but about why they even tried instead of diverting earlier. Might even be 100% done by the book but book needs changing (tho I doubt that, it's not exactly first case of "a lot of bad weather")
- jacquesm 1y agoOur definition of 'bad weather' is definitely changing as we gather more data. Besides regular weather (which airliners aim to avoid except during take off and landing) there are many other factors at play here. There are several almanacs that are used for fuel calculations & navigation, they are updated annually. The fastest jet stream (the aviation equivalent of the trade winds) recorded is north of 400 Kph, having that with you, against you or perpendicular to your flight path will have a substantial influence on fuel consumption and flight duration. I agree with you that it may well end up with a regulatory change but that's one of many possible outcomes here. I will definitely keep an eye out for the report on this flight's investigation. It is going to make for very educational reading.
- goodcanadian 1y agoNaively as an outsider, this situation seems like everything worked as intended? I don't remember all of the rules off the top of my head, but if you are ever landing with less than 30 minutes of fuel, something has gone seriously wrong. You are required to take off with sufficient fuel to fly to your destination, hold for a period of time, attempt a landing, fly to your alternate, and land all with 30 minutes remaining. If you are ever in a situation where you may not meet these conditions, you are required to divert immediately. In choosing your alternate, you consider weather conditions along with many other factors. This was, without question, a serious emergency. From the very brief description in the article, I would say they should have diverted to Manchester at least 25 minutes sooner than they did. I will include the GP's caution, however: I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
- hugh-avherald 1y agoIf you are ever in a situation where you estimate you will land with less than 30 minutes of fuel, you are legally obliged to declare a MAYDAY. One of the few situations where a mayday is legally required.
- nucleardog 1y agoThirty minutes. If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call. Mayday is a term enshrined in law. It is only to be used when people will die if you do not receive help. In the US, calling it inappropriately can be punished with up to 10 years in jail and a $250k fine. It's protected in this way because as soon as you call mayday, in many situations there are actions that must be taken by law or regulation. Other appropriate uses include things like "our plane is on fire" or "our wing just fell off and we can't steer the plane". As soon as you think you can't land with the fuel reserves you are _required_ to call mayday, other pilots are _required_ to clear the radio for you, and ATC is _required_ to provide any and all supported possible until you're on the ground. The investigation is not to figure out who to send to jail or something. The investigation is because a flight just came this >< close to having hundreds of people die. That fuel is there as a safety margin, yes. That's how everyone ended up walking off this plane instead of dying as the plane was ripped apart by some trees somewhere. That is good. But air travel did not become as safe as it with an attitude of "this hasn't killed anyone yet, all good". The fact there was an incursion into the safety margin should not be looked at as "eh, working as intended" but "holy hell we just came this close to disaster, what went wrong that almost killed all these people? how do we stop that happening again?". That is what an investigation will be looking to figure out. To put it in vaguely IT terms, this is something like... your application has started corrupting its database, but you have _a_ backup copy. On one hand, you can think "eh, we have a backup, that's what it's there for, who cares". On the other you can go "holy shit, any time we need to restore from the backup we narrowly averted disaster... how do we make sure we're not in that situation again?". The former is probably going to lead to irrecoverable data loss eventually. The second will have you addressing problems _before_ they ruin you.
- jenadine 1y ago> If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call. From the article, they did issue a mayday call, when the closest airport was presumably Edinburgh. Then they flew to Manchester and landed.
- kqr 1y agoIn safety-critical systems, we distinguish between accidents (actual loss, e.g. lives, equipment, etc.) and hazardous states. The equation is hazardous state + environmental conditions = accident Since we can only control the system, and not its environment, we focus on preventing hazardous states, rather than accidents. If we can keep the system out of all hazardous states, we also avoid accidents. (Trying to prevent accidents while not paying attention to hazardous states amounts to relying on the environment always being on our side, and is bound to fail eventually.) One such hazardous state we have defined in aviation is "less than N minutes of fuel remaining when landing". If an aircraft lands with less than N minutes of fuel on board, it would only have taken bad environmental conditions to make it crash, rather than land. Thus we design commercial aviation so that planes always have N minutes of fuel remaining when landing. If they don't, that's a big deal: they've entered a hazardous state, and we never want to see that. (I don't remember if N is 30 or 45 or 60 but somewhere in that region.) For another example, one of my children loves playing around cliffs and rocks. Initially he was very keen on promising me that he wouldn't fall down. I explained the difference between accidents and hazardous states to him in childrens' terms, and he realised slowly that he cannot control whether or not he has an accident, so it's a bad idea to promise me that he won't have an accident. What he can control is whether or not bad environmental conditions lead to an accident, and he does that by keeping out of hazardous states. In this case, the hazardous state would be standing less than a child-height within a ledge when there is nobody below ready to catch. He can promise me to avoid that, and that satisfies me a lot more than a promise to not fall.
- jama211 1y agoWell said, will think about asking this attitude towards my child, seems very helpful
- jacquesm 1y agoIf you haven't done so: please write a book. Aim it towards software professionals in non-regulated industries. I promise to buy 50 to give to all of my software developing colleagues. As for 'N', for turboprops it is 45, for jets it is 30.
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- faku812 1y ago[dead]
- nabla9 1y ago>One pilot who reviewed the log said: “Just imagine that whenever you land with less than 2T (2,000kg) of fuel left you start paying close attention to the situation. Less than 1.5T you are sweating. But this is as close to a fatal accident as possible.”
- ExoticPearTree 1y ago> How much fuel should they have landed with? I think about 30 minutes worth of fuel. Not knowing their flight plan, it could have been that Edinburgh was the first alternate and Manchester the second alternate.
- kokekolo 1y agoSimilarly naive outsider, but I've read things here and there. My understanding is that they should have declared mayday (emergency) and landed (potentially at another airport, potentially in the middle of nowhere) _way_ before so that when they have landed they still had 30 minutes or more of fuel in the tanks.