Grand Theft Auto: San Andreas default flight keys

Airplanes:

Arrow up: Increase throttle
Arrow down: Decrease throttle
Arrow left or A: Roll left
Arrow right or D: Roll right
W: Pitch down (dive)
S: Pitch up (climb)
Q: Rudder left
E: Rudder right
Move the mouse: Control stick
Mouse the mouse while holding right mouse button: Pan around airplane

Helicopters:

Arrow up: Increase collective
Arrow down: Decrease collective
Arrow left or A: Roll left
Arrow right or D: Roll right
W: Pitch down (dive)
S: Pitch up (climb)
Q: Tail rotor left
E: Tail rotor right
Move the mouse: Cyclic
Mouse the mouse while holding right mouse button: Pan around helicopter
(Note that the mission "Up, Up And Away!" features a Leviathan helicopter
with a magnet on the bottom which you can raise and lower with the vehicle
"Special Control Up" and "Special Control Down" keys, which are numeric
keypad keys 8 and 2 by default. After you complete this mission, a Leviathan
will spawn at your Verdant Meadows airstrip, and a Leviathan is also
available before that point at the airport in San Fierro. However, these
helicopters do not have the magnet; the magnet only appears on the helicopter
used for that specific mission.)

General controls:

2: Raise/lower landing gear (only on aircraft with retractable landing gear)
(CAUTION! On the Hunter military helicopter, 2 activates vigilante missions.
This helicopter does not have retractable landing gear.)

View controls:

V: Change basic view
Numpad 4: Rotate view left (for external views)
Numpad 6: Rotate view right (for external views)

Additional special controls which only apply to the Hydra jump jet:

Arrow up: Increase thrust
Arrow down: Decrease thrust
Numpad 8: Sweep nozzles back (Thrust makes you go forward)
Numpad 2: Sweep nozzles down (Thrust makes you go up)
Spacebar: Establish missile lock (hold and wait until targeting reticle is red for lock)
Left Ctrl: Fire missiles
Right Ctrl: Missile lock AND release flare (for spoofing infrared missiles)

Additional special controls which only apply to the Hunter military helicopter gunship:

2: Activate vigilante mission
Left Ctrl: Fire chaingun
Left Alt or Right Ctrl: Fire missiles