Ok... example, let me think.
I don´t know much about airplane physics, i only know car physics.
But i´m sure you need forces like drag, lift, weight and turbineforce.
You must separate weight to right, left, front and back.
dragforce=0.5*Cd*A*rho*v^2
where Cd is coefficient of friction what depends on the shape of the airplane.
A is the frontal area of airplane.
rho is air density whith is normally 1.29 Kg/m3, but you can make so that the air density drops when you are higher.
v is speed of the airplane.
You can start with turbineforce and dragforce, so when you take weight and lift away your airplane flyes straight.
Before you get velocity you must calculate acceletarion.
Here is example of calculating velocity:
set display mode 800,600,16 : sync on
Cd#=0.5 : a#=5.0 : rho#=1.29 : mass#=5000
time=timer()
turbineforce#=80000 : rem in newtons
do
timestep#=(timer()-time)/1000 : time=timer()
dragforce#=0.5*Cd#*A#*rho#*velocity#^2
totalforce#=turbineforce#-dragforce#
acceleration#=turbineforce#/mass#
velocity#=velocity#+timestep#*acceleration#
cls : print velocity#
sync : loop
This is good way to start making your game.
My Cd, A and mass values may be wrogn, but you can find them from internet or you can test and get good values.
And remember that airplane is steered by wings, so don´t make code like: (if leftkey()=1 then turn camera left)
instead try moving those wings and get airplane rotate trugh physics.
It´s maybe hard, but it´s lot better way to do.
