I once saw an Airbus A300-600 with a 4 foot block of ice in a main tank opened for a repair on a B-check soon after a flight.
Seen the same in the trim tank of an A310 in DXB.
Currently working with an AOC whose pilots have to drain fuel on pre-flight; they hate it because, due to the size of the aircraft (F406), they are getting covered in fuel.
