Wait, FMCs aren't MCs? Huh? 
(serious)
Unless they're somehow not MCs, they're legal. I might be very wrong, but if they remain airborn their ability to kill stuff is greatly reduced, right? These events are almost entirely about killing things, although this one does penalize dying all the time.
Technically, no they aren't MCs, cuz they have their own entry in the "unit types" sections, same way as bikes aren't infantry. "Jump" and "jetpack" are modifiers to other unit types, but "bikes" and "FLying Monstrous Creatures" are their own thing. So for instance, you can have jump infantry, and you can have both Jump MCs and Jepack MCs (Riptides) which
are MCs, but FMCs are not MCs any more than bikes are. Again, technically.
Classic RAW vs RAI, you can only assume that if it came up in a FAQ whether Jaws of the WOrld WOlf affected non-swooping FMCs, they'd say they would, but atm, if you follow RAW, it doesn't.
Anyway, no, Chase, I don't think remaining airborne reduces a FMCs ability to kill stuff much, at least not if they brought their guns. Arguably, they can do more dmg with Vector Strike. Now, they have to come down to charge a unit, but then you have the problem that they can charge who THEY want, WHEN they want, but no one can charge them first.
I don't think I'll attend this event, so I don't have a dog in this fight, but I think if you allowed FMCs it would be very, very unbalancing. I get that it's not really supposed to be that balanced an event to start with, but there just wouldn't be any point in playing a non-FMC.
That said, a lot of the cooler "MCs" are FMCs, like the bloodthirster, so I'd probably just let people play FMCs as jump MCs. Then they'd still have a pretty big movement advantage, but they wouldn't just be untouchable the way actually Flying would make them.
