A premiere for me...

[Arthanor]

Medium scout is likely the only vanilla ufo for which this could happen. It's small enough that a large explosion will shred it and all the aliens inside, and the crew is small enough that they might all be in to get shredded. On a large scout, at least one alien should be safely spawned outside.

There are a few modded UFOs to which that could happen, first to come to mind is the old version of the small fighter UFO from Solarius, with 2 power sources, a small footprint and a small crew.

[new_civilian]

Medium scout is likely the only vanilla ufo for which this could happen. It's small enough that a large explosion will shred it and all the aliens inside, and the crew is small enough that they might all be in to get shredded. On a large scout, at least one alien should be safely spawned outside.

There are a few modded UFOs to which that could happen, first to come to mind is the old version of the small fighter UFO from Solarius, with 2 power sources, a small footprint and a small crew.

Which it was (see first post, it was a fighter from a mod.) 

[Warboy1982]

it's a recent(ish) addition, if all the aliens are killed in the power source explosion, this happens, just as it did in tftd, just like hobbes said. we saw no reason not to apply it to ufo as well.

[hellrazor]

it's a recent(ish) addition, if all the aliens are killed in the power source explosion, this happens, just as it did in tftd, just like hobbes said. we saw no reason not to apply it to ufo as well.

Well it makes total sense
Need to make a fun mod were the entire alien crew spawn near the powersources
Autorecovery ^^

[Solarius Scorch]

Wow, it was I who made the Fighter, and I've downed hundreds of them, but never had this total wipeout.

As for the original game, this wouldn't happen because the aliens can only die because of the UFO Power source explosion, and all UFOs are set to have some of its crew be spawned outside. The Fighter is specifically designed to not be like this (because it's a small craft designed for defence, and certainly not for ground missions).

But I wonder what would happen in the original game if it had such a UFO and everyone died inside. Would the game just crash?

[new_civilian]

It would maybe end after the first turn... 

[Solarius Scorch]

It would maybe end after the first turn... 

Yeah, I'd expect them to build in some sort of a fail safe.

PS. Civilian, I hate TFTD too.