As stated above High Intensity Radio Transmission Areas.
Avoidance was mandatory for military aircraft with the radius of avoidance depending on the bands in which it transmits and the susceptibility of the specific aircraft type to each band. Electronics are affected to varying degrees and the effect on the body is 'experimental'. Would you put your gonads in the microwave?
For civvy aircraft I think it's your call rather than mandatory, but I refer you to my previous comment.