On the way across the pond last week a thought occurred to me. Being on a 777 and miles from any land....
If there was a engine failure AND depressurisation event then is the flight planned to allow etops flight at max time at 12-14k altitude? Surely thats a massive amount of fuel and complex planning needed?
In EU-OPS their is a provision for these circumstances called "additional fuel". It's required if, taking into account the more fuel consuming of depressurization
or engine failure, the airplane cannot make it to an adequate aerodrome and land with the normal fuel reserves (contingency, alternate, final). The minimum additional fuel is required shall permit diversion to this adequate aerodrome, hold there for 15 min and then make an approach and landing.
Reference: EU-OPS 1.255 Appendix 1