Hello to everybody, I'm a total newbie and just a huge fan of aviation with limited technical knowledge. But I'm a very curious person, I have a question, and I thought it was better to ask the professionals.
(I think) I know that an aircraft has an optimal cruise altitude and speed, and that different altitudes and speeds will significantly shorten its range and endurance (please correct me if I'm wrong.) I was thinking in an scenario where a modern jetliner (let's say an A350 or B787 or the like) experiences decompression during an intercontinental flight above the ocean so the crew is forced to descend to safe altitude (that's 8,000 ft I think?)
My question is basic: how much would this diminish its range or endurance? Would this aircraft still be able to land in an alternative airport if it happens "deep into the ocean"? (I mean, are transoceanic flight plans calculated predicting this possibility?) And, if you're so kind, how would all of this affect its speed?
I know there are performance tables to calculate all this, but I've been unable to find any and I'm not sure I would be able to properly use them. So, since I wouldn't like to bother you too much, just a "back of the envelope" estimate will be enough.
Thank you all in advance, sorry if I made any stupid error (quite probable!) and please moderators move this post if it isn't in the correct forum.