14 ms·

My understanding is that's the common ex post rationalization that arose to try to come up with a plausible-sounding reason for this idiotic rule.

JonnieCache 13y ago
My favourite theory was that cellphones above the clouds could connect to too many cell towers at once, making triangulating your location impossible. Conveniently forgetting that they have a live update of your exact position from NORAD/FAA/etc...
- Zigurd 13y ago
  The "too many handovers too fast" thing might have been a problem in the '80s, and I have never heard of a documented case of that.
  - mikeash 13y ago
    My understanding is that the problem isn't with the speed of the handovers, but rather with the fact that the horizon is a major block to radio signals, and the horizon is much farther away when you're at altitude. Older networks were designed around the fairly reasonable assumption that a cell phone would only ever be able to talk to adjacent cells, because anything farther away would be over the horizon. So you might be able to talk to both A and B at the same time, but you couldn't talk to C without first losing contact with A. Raise the phone a few thousand feet in the air and this assumption goes out the window, confusing the network. There's an amusing story of a pilot who called up his family to let them know he was almost home and ended up getting billed for the call (at expensive 80s rates) a bunch of times because several different towers all thought they were running the call. There's certainly no problem today, anyway.
    - Zigurd 13y ago
      > Older networks were designed around the fairly reasonable assumption that a cell phone would only ever be able to talk to adjacent cells, because anything farther away would be over the horizon That can't possibly be true. Spectrum re-use in distant sites could in theory have some effect on the call but differences in signal strength would make significant effects unlikely. Also, that story about the pilot must also be apocryphal. A handover is a handover, and there is only one "winning" decision. Not to mention that CDRs don't work that way. Lots of civil aviation pilots use mobile devices in the air without problems for the user or network.
      - mikeash 13y ago
        You may be right about the story, but I don't really see the obstacle to it happening. If you initiate a call in the air, you could easily not be able to communicate with the cell directly below (since they don't radiate much signal upwards) while being able to talk to two that are adjacent to it. Since those two cells would never have a reason to communicate in normal operations, confusion ensues. I know that lots of pilots use mobile devices now, but we're talking ~30 years ago.
- teraflop 13y ago
  Well, I always heard that the problem was rapid handoffs between towers causing a lot of extra load on both the cell network and the phone itself. I can tell you anecdotally that on a few of occasions I haven't put my phone in airplane mode during a flight, and it seems to drain the battery muck more quickly than normal.

JonnieCache 13y ago

My favourite theory was that cellphones above the clouds could connect to too many cell towers at once, making triangulating your location impossible. Conveniently forgetting that they have a live update of your exact position from NORAD/FAA/etc...

Zigurd 13y ago
The "too many handovers too fast" thing might have been a problem in the '80s, and I have never heard of a documented case of that.
- mikeash 13y ago
  My understanding is that the problem isn't with the speed of the handovers, but rather with the fact that the horizon is a major block to radio signals, and the horizon is much farther away when you're at altitude. Older networks were designed around the fairly reasonable assumption that a cell phone would only ever be able to talk to adjacent cells, because anything farther away would be over the horizon. So you might be able to talk to both A and B at the same time, but you couldn't talk to C without first losing contact with A. Raise the phone a few thousand feet in the air and this assumption goes out the window, confusing the network. There's an amusing story of a pilot who called up his family to let them know he was almost home and ended up getting billed for the call (at expensive 80s rates) a bunch of times because several different towers all thought they were running the call. There's certainly no problem today, anyway.
  - Zigurd 13y ago
    > Older networks were designed around the fairly reasonable assumption that a cell phone would only ever be able to talk to adjacent cells, because anything farther away would be over the horizon That can't possibly be true. Spectrum re-use in distant sites could in theory have some effect on the call but differences in signal strength would make significant effects unlikely. Also, that story about the pilot must also be apocryphal. A handover is a handover, and there is only one "winning" decision. Not to mention that CDRs don't work that way. Lots of civil aviation pilots use mobile devices in the air without problems for the user or network.
    - mikeash 13y ago
      You may be right about the story, but I don't really see the obstacle to it happening. If you initiate a call in the air, you could easily not be able to communicate with the cell directly below (since they don't radiate much signal upwards) while being able to talk to two that are adjacent to it. Since those two cells would never have a reason to communicate in normal operations, confusion ensues. I know that lots of pilots use mobile devices now, but we're talking ~30 years ago.
teraflop 13y ago
Well, I always heard that the problem was rapid handoffs between towers causing a lot of extra load on both the cell network and the phone itself. I can tell you anecdotally that on a few of occasions I haven't put my phone in airplane mode during a flight, and it seems to drain the battery muck more quickly than normal.