Radio spectrum, according to the U.S. Department of Transportation, is divided into different frequency bands that have been allocated for data, voice, and wireless communications used by a variety of different industries. Aircraft radar altimeters operate within 4.2–4.4 GHz, the lower half of which falls within the C-Band—a frequency range from 3.7–4.2 GHz where the combination of the range of signal transmissions and capacity are optimum.

A graphic shown by AVSI's Andrew Roy during a Dec. 7 NBAA webinar shows power levels of the previous satellite emissions that were occurring in the 3.7–3.98 GHz band that 5G stations in the U.S. will start using next year.

The 5G wireless networks scheduled to be switched on by AT&T and Verizon next month will occur within the 3.7–3.98 GHz frequency range, close to the altimeters. As the FAA indicated in its Dec. 7 AD, while it has heard concerns from airlines, the FAA, and aircraft OEMs over the potential interference issues posed by the deployment of 5G in the C-Band, it has not yet been presented with data or information that shows altimeters are not susceptible to interference.