The maximum time you can be away from a suitable landing spot depends on the ETOPS certification (or 60 minutes if you don't have one). The certification is spe

The maximum time you can be away from a suitable landing spot depends on the ETOPS certification (or 60 minutes if you don't have one). The certification is specific to the type of plane and operator. A modern 777 at most airlines for example has an ETOPS rating of 180 minutes. That's 180 minutes of flying with a failed engine. So you have to take into account whether you can maintain altitude on 1 engine. Most of the time you can't, you'll be flying lower. Which means slower speed, so the calculation is 180 minutes at that speed.