Here's the idea: Building a "jet fighter" that can operate in extended combat conditions with no atmosphere without losing air superiority in atmosphere.
It's not going to have both traditional jet engines and rocket engines. The jet engines would be deadweight in purely space combat, and the rocket engines (oxygen tanks included) add extra weight in atmosphere. Worse, an engine that needs to expel matter to produce momentum risks running out of fuel in an extended fight.
In this setting, practical "impulse engines" that push against the fabric of space-time haven't been invented yet and probably won't reach the market for another 100-200 years.
This calls for an electromagnetic engine that emits a massive volume of photons with combined momentum per second comparable to a late 2010s-era jet fighter engine.
Assume a suitable power source is already available and the combined thermal profile (generator + engine) is comparable to a modern jet fighter.
The main challenge: figure out an appropriate wavelength for the engine output that doesn't burn, cook, blind, or irradiate the ground crew. The hazard zone behind the engine should be comparable to a traditional jet engine - or smaller. Additionally, it must not produce EMP-type effects that damage or interfere with electronics further than 100 meters away in a cone shape behind the engine.
The volume of photons would be massive considering that each photon has only a tiny amount of momentum.
Obviously, any sort of ionizing radiation is out of the question due to environmental damage and health concerns. Visible-spectrum light is a poor choice because it would instantly blind anyone who happens to look at the engine the wrong way.
Infrared can't be used due to the known health hazards of intense infrared radiation (https://en.wikipedia.org/wiki/Infrared#Health_hazards): "Strong infrared radiation in certain industry high-heat settings may be hazardous to the eyes, resulting in damage or blindness to the user. Since the radiation is invisible, special IR-proof goggles must be worn in such places."
A microwave engine is a bad idea because the engine output might knock out electronics from miles away in a manner comparable to EMP weapons. NOTE: the engine in question is open-ended, not a closed reflective "EM-drive" chamber.
This leaves only extremely low frequency/long wavelength radio waves as the remaining option.
The question: Is it possible to pick a wavelength long enough to avoid causing thermal or optical damage to the ground crew and nearby population while also preventing EMP-type damage to electronics?