They are the disasters,
, for monorail a UFO land over the track and itīs blowed off by the X-Com, in water there are submarines(i saw them but never saw an attack over a ship), a smaller UFO can colided with your road units, a zepelin crash over an airport and if a plane try to land in these airport before removed, u will got a plane crash
Anyway, i didnīt know of the X-com HQ
