P-51's in movie "Empire of the Sun"

JN-4 "Jennies" served as German and British/US fighters in the
WWI movies of the 20's and 30's. Just a splash of paint and
a roundel made it a Sopwith Camel, or a black cross and it was
a "Fokker".

Hardly. An amazing number of actual WW1 aircraft were used in early movies.
Later films used aircraft that certainly looked a lot closer to the actual
types than JN 4s. Fokkers were made from modifying early Travel Aires which
were remarkably similar to the later Fokkers even being built of steel tubing
and using elephant eared ailerons. Rotary engine types were duplicated with
radial engine aircraft and Garland Lincoln went to great efforts to duplicate
Nieuports.

John Dupre'