When Axel's biplane crashes into the pond, the stunt pilot's goggles are still correctly in place as the aircraft settles. In the closeup, Axel's goggles are suddenly askew on his face from the "impact".
After Ezra crashes trying to do the loop Waldo takes off in a plane to chase of the spectators. The pilot is wearing goggles. In the subsequent shots where Waldo buzzes the crowd he is not wearing goggles.
Throughout the scene where Mary Beth is wing walking, she is standing up while the dummy that was her stand-in was kneeling. So from one scene to the next the figure was standing, kneeling, standing, etc.
When Ezra and Waldo drive up to the farmhouse in Ezra's pick-up it is very obvious that the truck looks far too old for the 1920's time frame of the movie. In the late 1920's that truck would have been new or nearly new. Instead, it is obviously 40 or 50 years old (which is just about exactly the age it would have been when the movie was released in 1975).
When Waldo is refueling his plane from the can delivered to him by the little boy, his hand is seen resting for some time on what would presumably be a very hot exhaust pipe.
(at around 1 min) When Axel is flying over a town with Mary Beth out on the wing of the plane, there are many modern cars visible on the towns' streets.
A modern power line tower can be seen during the dogfight sequence between Waldo and Ernst.
Ernst Kessler's plane in the airshow scenes is a modified Bücker Bü 133 Jungmeister, a design that was built starting in the 1930s.
The Jungmeister was a smaller, single-seat version of the the Bücker Bü 131 Jungmann, which was a two-seat basic trainer.
The Jungmeister was originally powered by a 160 hp radial engine. The movie airplane was re-fitted with a modern, horizontally-opposed engine, such as a Lycoming or Continental.
The Jungmeister was a smaller, single-seat version of the the Bücker Bü 131 Jungmann, which was a two-seat basic trainer.
The Jungmeister was originally powered by a 160 hp radial engine. The movie airplane was re-fitted with a modern, horizontally-opposed engine, such as a Lycoming or Continental.
When Waldo Pepper walks out on the wing to practice his first wing walk, the shadow of the camera can be seen on the plane.
Following the scene of Waldo's initial wing walk, there is an aerial view of four planes flying but there are five plane shadows on the ground. The fifth shadow is of the camera plane.