47 CFR 87.107 requires that radios transmitters in aircraft broadcast an identification number, and the allowed forms of identification aren't permissive enough

47 CFR 87.107 requires that radios transmitters in aircraft broadcast an identification number, and the allowed forms of identification aren't permissive enough for non-registered aircraft. ADS-B out is still relatively new (especially in aviation terms) so I expect we'll see this continue to evolve.