The best way to approach this kind of composite shot is to find the footage of the airplane first then figure out the camera angle and position, then shoot your shot with your actor. If this were my project I'd draw a storyboard of the shot then find stock footage of an airplane that matched the storyboard, then carefully figure out the camera position and shoot my actor.
If you have already shot the actor then you need to find some footage that has a plane shot from the same angle. Preferable both shots are locked off, but as you gain some experience you'll be able to do some match moving using tracking tools available in AE and or Mocha to line up your shots. The very hardest part is matching the angle and perspective. Perspective is controlled by camera position not focal length so if you have a shot of an airplane where the camera is pointing up towards the sky at 15º you'll need a shot of your actor with the camera pointing up at about 15º to have any chance of a believable composite. As long as the camera position is correct you could shoot the actor with a medium or wide lens and use stock footage shot with a telephoto. As long as you properly scale the footage of the plane so the size closely matches what you would see if the plane was actually there the shot will work just fine. I almost forgot to mention lighting. You also have to pretty well match the time of day and angle of the sun so the lighting will match unless the plane is mostly just a dark spot in the sky.
The technique you use depends entirely on the shots you have to work with. The easiest replacement would be to use a procedural matte or keying with the actor or the plane shot against a blue sky. Then you simply layer the shots and scale the plane footage to match. Other techniques include manually rotoscoping a hole in the sky for the plane to fly through and filling the hole with the plane's sky. You'll have better luck if you do not just cut out a plane and make a freeze frame and then animate the plane's position by animating position. You can pull this off if the plane is very far away.
Another option would be to shoot your actor with a moving camera being careful to make sure you have created a shot that can be Camera Tracked. Then you Camera Track the shot in AE, add some reference solids, export the layers and camera to a C4D file, then place a plane model in the C4D project and animate it's position across the sky. If you've added enough reference solids to the AE comp you should be able to figure out where to put the plane in C4D.
More details and a screenshot of what you are trying to do and how you are going to frame your actor would help point you down the shortest road.
Ok. Thankfully I havent shot any footage yet. Im still prepping it. I will shoot the shot on location. Then later try to match the airplane footage. There is an airplane nearby so Ill try to pick a spot where the planes are flying in a specific direction from teh same angle. But I am trying to learn how to composite the plane footage into my shaky footage. I dont think I could get a steady shot for the idea I have in mind. Are there any tutorials that could help composite (steady) plane footage to slightly unsteady sky footage? I would be really grateful. Thanks for all the help. In around a month I should have the project finished so I think I have time. Thanks again
*airport not airplane sorry
Make sure your shaky shot has something in it that you can track. Test this by shooting some shaky footage and compositing some text or a square into the scene.
Here are some resources on motion tracking: Tracking and stabilization motion workflows in After Effects