Even if the pilots believe the false warnings, evading phantom planes poses no safety risk to passengers. Thus, the radar is entirely beneficial, which strengthens the author's argument.

This is irrelevant. We're comparing planes with a radar to planes without, but there's no difference while the planes are on the ground. So this doesn't tell us anything useful.

This still doesn't allow us to judge the radar's usefulness, or how likely a warning is to be true or false. So, this doesn't affect the argument.

Most warnings are invalid, but do those invalid warnings pose safety risks to passengers? This doesn’t tell us, so it doesn't make any difference to the argument.

This explains the mechanism behind the radar, but it doesn't explain whether false warnings pose a safety risk. That means that without further information, it's irrelevant to the argument.