You are quite right Bealzebub
I was being vague about ETOPS but it was for errotechs sake.
As his questions about diversion change from engine out to loss of pressurisation. Aircraft also divert due to full toilet tanks but that question hasn't been muddled into this thread yet.
BUT if you have an engine failure on a light twin ,757,767,A330 etc and also a loss of cabin pressure therefore decend to 10k feet to keep pax alive and you are at 179 mins flying from nearest diversion(this 179 minutes is calculated at criusing alt) there is a high possibility that the aircraft will not enough fuel on board to fly this distance.Depends what flight phase you are in when these disasters strike But we are talking about 2 or 3 major failures happing at once...A very bad day at the office.
I have fueled planes ( 767) for non pressurised ferry.
eg Normal fuel for trip with pax cargo around 13,000kgs unpressurised ferry trip no pax no cargo... 20,000kgs of fuel
Hope i appear less vague this time
Bolty
Question for Aerotech.. Are you a big MS Flight Sim fan??