In large commercial aircraft there is almost always an APU (Auxiliary power Unit) in the tail. This is a small jet connected to a generator for ground power, you may be looking at it's exhaust.
It is called the horizontal stabilizer. The elevators are mounted on the tail end of it.
The effect of a hole on a paper airplane would depend on the type of paper airplane the hole is on, and where it is on the aircraft.
Elevators. They control the pitch of the aircraft.
an airplane
through a small hole called a vent beneath their tail
It part of the tail.
Tail will tilt up
empennage
So that it can land like an airplane
in a conventional airplane it connects the wing to the control surfaces in the tail.
Did you really mean "airplane" - or did you mean airline . -If airline it is Qantas.
Dig a hole, place your head in said hole, cover up hole.