5G Restrictions Set To Affect At Least 90 U.S. Commercial Airports

5G tower
Credit: Niels Wenstedt / BSR Agency / Getty Images

Airline industry stakeholders are working to assess the real-world ramifications of new flight restrictions linked to the 5G wireless network rollout starting Jan. 19, but early indications suggest potentially significant disruptions at scores of commercial airports across the U.S. 

The FAA early Jan. 13 published nearly 1,500 notices to air missions (NOTAMs) linked to the introduction of 5G services over frequencies in the C-band spectrum that are close to ones used by radio (radar) altimeters, which measure altitude above terrain and feed other aircraft systems.  

The NOTAMs warn of potential interference at more than 1,300 specific airports. About 100 of them prohibit specific low-visibility procedures into certain runways, including “special authorization” Category I as well as Category II and III and Required Navigation Performance approaches. 

Interference from the 5G equipment “could cause the radio altimeter to either become inoperable or present misleading information, and/or also affect associated systems on civil aircraft,” the FAA said in a December 2021 airworthiness directive addressing the issue. 

“The receiver on the radio altimeter is typically highly accurate, however it may deliver erroneous results in the presence of out-of-band radio frequency emissions from other frequency bands,” the FAA said. “The radio altimeter must detect faint signals reflected off the ground to measure altitude, in a manner similar to radar. Out-of-band signals could significantly degrade radio altimeter functions during critical phases of flight, if the altimeter is unable to sufficiently reject those signals.” 

An initial analysis of the NOTAMs by the Air Line Pilots Association (ALPA) found at least 90 U.S. airports with commercial passenger service, and several more with cargo-only service. ALPA said Jan. 13 that it was evaluating the NOTAMs and working to quantify their real-world ramifications once Verizon and AT&T begin 5G deployment on Jan. 19. 

“[Flight] cancellations and operational disruptions will be a reality as we work to clean up the mess made by the” Federal Communications Commission (FCC), ALPA President Joe DePete said. 

Aerospace Industries Association VP-Civil Aviation David Silver said the group’s “technical experts” were reviewing the NOTAMS as well.

“We know there is still a lot of work to be done to resolve these issues in commercial aviation, and to begin addressing issues with general aviation and helicopters,” he added.

Wireless provider T-Mobile offers 5G services in the U.S., but it does not use C-band.

While AT&T and Verizon have delayed the roll-out date twice and agreed to six-month buffer zones around 50 airports, aviation industry stakeholders say the remaining unknowns present significant safety risk. The NOTAMs’ restrictions apply unless operators have demonstrated their radar altimeter is “proven to be accurate and reliable,” the FAA said. Airports with buffer zones are still subjected to some NOTAM restrictions. 

“[At] this time, no information has been presented that shows radio altimeters are not susceptible to interference caused by C-Band emissions permitted in the United States,” the agency said in its December 2021 directive. 

The wireless industry points to successful deployments in other countries and an absence of evidence that aviation operations there have been affected as validation that U.S. aviation stakeholders are overreacting.  

The FAA said technical differences in the deployments, including allowable 5G equipment power levels and restrictions on antenna angles in countries such as France, make direct comparisons difficult.  

Wireless trade association CTIA counters that much of this is not true, saying authorized power levels in Europe are higher than the U.S., and antenna deployments are following the same rules as in France. 

Sean Broderick

Senior Air Transport & Safety Editor Sean Broderick covers aviation safety, MRO, and the airline business from Aviation Week Network's Washington, D.C. office.


How could this happen? The frequencies of RAs are known for many years. Why are the 5G frequencies allocated so close to the RA frequencies? The newcomers have to step back and make sure that their "new stuff" does not interfere with established applications.
The biggest problem seems to be the frequency spacing between the radio altimeter spectrum and neighboring 5G spectra. Consequently, the greatest risk of interference should be found in Japan - see Fig. 4.1. "3GPP Bands and Spectrum Allocations Near the Altimeter Band" on page 19 in https://www.5gamericas.org/wp-content/uploads/2021/07/Mid-Band-Spectrum-and-the-Co-Existence-with-Radio-Altimeters.pdf . What is the experience there?
The major problem: 5 Attorneys are heading the FCC, period.
Their school curriculum does not include technical training.
Why do we appoint attorneys to a position that would require expert technical knowledge?