i was worried reading these scary storys of these missions and finally got to them last night (finished the story and hidden lairs 100%) i finished the flying machine first try. just knock out the main towers as soon as you can shoot them. and it took 2 tries for the tank mission because i forgot about the canon outside the first room
over all, ive had little trouble getting 100%. some of the sneaky missions were a bit annoying but not really hard. just gotta figure out the best way to do it.