Items on an aircraft you never want to see

Aircraft carry several pieces of equipment that passengers rarely get to see, or even suspect might be on board.

"Passenger restraint" is the polite term for handcuffs, and you can bet they're carried.

Crew will break them out to restore order if a passenger looks like getting out of hand and threatens violence to another passenger or themselves.

Defibrillators are not mandated medical equipment but many airlines carry them.

Qantas was one of the first to introduce defibrillators on all its aircraft and all US-based commercial airlines are now required to carry them.

They're also carried on all Emirates, British Airways, Lufthansa and Virgin Atlantic flights.

If there's a sky marshal on board, hope you never find out who it is because it means things just got ugly.

Sky marshals maintain a very low profile; they are there to maintain the safety of the aircraft and its passengers mainly against terrorists, they carry side arms but they will only spring into action in an extreme situation.

They will not assist cabin crew to subdue a drunk, unruly passenger for example, that's too common, and it might be a ruse intended to establish whether there is a sky marshal on board.