My problem with Chain Lightning.

I wish I could engage in this discussion, but I have yet to see the film. It is on my watchlist, however.

That would certainly be a big concern. I don't think the location for the test flights in the film was specifically spelled out, but it was based on the supersonic testing that pilots like Chuck Yeager did at what is now Edwards Air Force Base in California. Yeager first broke the sound barrier over the Mojave Desert, and in general the pilots were flying away from populated areas. Such areas were also chosen for reasons of secrecy.

Another example they showcased in the film was the long distance test flight from Alaska to Washington, D.C. - while much of this flight was supposed to take place over the North Pole, it would have to eventually cover major cities. I've never heard of real test flights like this, so I assume it is purely fictional.

Not sure if you saw it, but before the film TCM showed a 20-minute short on the making of Chain Lightning, as part of the WB Anniversary programs. (The short is somewhat facetiously titled Jet Jockeys in Love.) It was really interesting to see the design of the 50's-era special effects that went into the film for all of the futuristic aviation technology of the time. Warner Brothers put a great deal of effort into creating the model and full-scale planes and developing new sound effects for the jets.