A fire on a shuttle or any manned spacecraft is pretty deep shit really. It takes up all the oxygen f**kin quickly and without gravity it can spread much quicker although the lack of burnables might slow it down a bit.
As for the fly shizzle I'm pretty sure that because of the train's huge amount of energy and the fly's tiny amount means that the train will decelerate the *tiniest* amount but will in no way stop.
And earlier I was thinking about why the fly can't just instantly go from 100m/s to 0 and I really can't think of a reason. I know it should have to decelerate then accelerate but when the train has that much more energy surely the fly changes speed so quickly it cannot be measured in time as it is an instant event?
Oh and I think a fly performs a flip just before it reaches the ceiling, at least that's what I think I've seen. But who cares all flys deserve to die, I like my spiders :)