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.
through a small hole called a vent beneath their tail
an airplane
It part of the tail.
Tail will tilt up
empennage
So that it can land like an airplane
The up and down movement of an airplane's nose is called "pitch." Pitch refers to the angle of the aircraft's nose relative to the horizon and is controlled primarily by the elevators on the tail of the airplane. Adjusting pitch affects the aircraft's ascent or descent during flight.
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.