A fairly simple method would be to do this, although I don't know how realistic it would be:
The following forces apply to the plane at any one time:
Force of Gravity (mass*acceleration due to gravity) (always towards ground)
Force of Lift (due to flow of air over wings, proportional to forwards velocity of aircraft and always in the 'up vector' relative to the aircraft)
Force of Friction (due to air resistance - dependent upon the square of the velocity and the cross sectional area of the moving object perpendicular to the direction of movement - a simple constant should suffice multiplied by the velocity of the aircraft squared)
Force of Thrust (due to propeller/jet etc in direction 'forwards' relative to aircraft.)
Then combine these forces by adding them together (vector addition so you will get components in each direction x,y,z) and apply the force to the aircraft as an acceleration to the aircraft.
Play around with something like that to get started, otherwise there should be plenty of information online on how to simulate aircraft motion.
The following forces apply to the plane at any one time:
Force of Gravity (mass*acceleration due to gravity) (always towards ground)
Force of Lift (due to flow of air over wings, proportional to forwards velocity of aircraft and always in the 'up vector' relative to the aircraft)
Force of Friction (due to air resistance - dependent upon the square of the velocity and the cross sectional area of the moving object perpendicular to the direction of movement - a simple constant should suffice multiplied by the velocity of the aircraft squared)
Force of Thrust (due to propeller/jet etc in direction 'forwards' relative to aircraft.)
Then combine these forces by adding them together (vector addition so you will get components in each direction x,y,z) and apply the force to the aircraft as an acceleration to the aircraft.
Play around with something like that to get started, otherwise there should be plenty of information online on how to simulate aircraft motion.