There are a number of miniature aircraft techniques on display in this movie with the special effects supervised by Vernon L. Walker.
The first model we see is of a Stearman C2B. It can be seen flying against a real sky in the background as well as using a traveling mattes for the shots where it is flying over the heads of live action extras. Later shots the same model is being photographed with a rear projection screen in the background as it does barrel rolls. It also crashes into the roof of a barn with the entire landscape being a miniature.
The next model is of an advanced pursuit plane. This time the model is actually meant to be a model as it is in a wind tunnel and you can get an idea of its size as in a couple of shots the actors hold it in their hands. The aircraft is modelled on the Hughes H1 which is what is being used for the full size aircraft.
We see this model later in two versions against a rear projection screen in a number of flying and diving shots. In one sequence a wing comes off and it crashes into ground, another full miniature landscape. This aircraft also features a model that has moving landing gear which is shown folding up and coming down with a story point where it is stuck not fully extended. In this climactic sequence there is also a model Ryan ST-A.
There is also some shots using a model Fairchild 24C8C also shot doing loops against rear projected backgrounds. It would be interesting to see the rig used to perform the loops as it could not simply be wires hanging from above.
All in all quite a fascinating model aircraft movie from a miniatures point of view if not particularly realistic.
