5G C-Band, You Are NOT Cleared for Takeoff

Changes to 5G Rules Still Needed to Protect Aviation

The 5G C-Band signals telecommunications companies activated in early 2022 may interfere with equipment airline pilots use to safely operate commercial flights every day.

That’s why, when AT&T and Verizon were scheduled to turn on 5G C-Band signals in the United States, frontline aviation workers and industry stakeholders called for a delay, and it’s why we are continuing to press for critical changes to the current rules to ensure long-term safety. U.S. commercial aviation is the safest mode of transportation in the world, and that didn’t happen by accident. As a nation, we made it a priority—and ALPA intends to keep it that way.


In 2018, the Federal Communications Commission (FCC) auctioned licenses for use of the 5G C-Band spectrum to telecommunications companies. ALPA and others in the aviation community immediately responded by urging the FCC to fully analyze the potential impact on commercial flight safety systems. These C-Band transmissions are dangerously close to the frequency used by radio altimeters onboard commercial aircraft to determine how high the aircraft is flying. Interference from 5G signals can result in the loss of radar altitude information or, worse, incorrect radar altitude information that provides hazardous and misleading information.

ALPA and other aviation leaders offered to assist the wireless industry in conducting a comprehensive study on the effects of these proposed transmissions on aircraft navigation systems, but no such study has taken place. We have been warning these stakeholders since 2018 that the 5G plan would interfere with airplane radio altimeters, but they ignored us. 

In 2020, RTCA published a paper that evaluated the interference risk. That report has since been validated by the Federal Aviation Administration (FAA) and multiple aviation safety regulators globally and demonstrates that radio altimeter interference by 5G broadcast in C-Band is a safety risk because the data generated onboard the aircraft is often utilized by other systems, such as terrain-avoidance systems.

In the United States, wireless broadband deployment was originally scheduled to begin on December 5, 2021. After high-level talks, mobile wireless agreed with the FAA to delay broadcast of C-Band 5G until January 19, 2022. With just hours before the deployment, mobile wireless further agreed not to turn on 5G transmitters within 2 nautical miles of airport runways.

Verizon and AT&T turned on their C-Band 5G networks in the United States on January 19, 2022. Although they did agree to once more delay broadcast of 5G from some locations near airports, the changes did not eliminate the need to immediately activate directives and notices for airline operations to maintain safety. Pilots have been asked to report radio altimeter anomalies to their airlines and to ALPA through our DART system

What’s Happening Now

In the time since C-Band 5G transmissions were activated, airlines have been upgrading radar altimeters to improve their ability to tolerate interference. The FAA is strongly urging airlines to complete the updates by July 2023, so that aviation safety can be assured when mobile wireless goes to full power at that time. Aircraft that have not been upgraded will have severe operational restrictions placed on them. Additionally, the FAA has recommended slight changes to the FCC C-Band rules to ensure that the mobile wireless industry’s use of 5G is compatible with the upgraded radar altimeters.

On November 15, 2022, ALPA joined many other aviation industry organizations in a letter that calls on the White House National Economic Council, FCC, National Telecommunications and Information Administration, Department of Transportation, and Department of Commerce to support the FAA’s recommendations. Read the letter.

The recommended changes include:

  1. Ensuring that antennas direct most of their power downward, away from aircraft flight paths;
  2. Requiring a lower unwanted emissions limit for 5G base stations in the band directly used by radar altimeters; and
  3. Mobile wireless working in cooperation with the FAA to modestly reduce power near key airports.

These changes would not significantly impact 5G operations and, in fact, are already being voluntarily followed by current mobile wireless deployments.

However, the FAA has also said that without permanent changes to the FCC’s 5G rules, the newly upgraded radar altimeters will still be inadequately protected, meaning that the current upgrade investments could be rendered useless. It would take years before radar altimeter equipment can be designed, manufactured, certified, and installed to meet the unrestricted transmission rules allowed by the current rules.

Flight safety continues to be at risk. The reliability of air travel is at risk. We all want 5G, but not at the expense of aviation safety. For pilots, this isn’t about politics or profit; it’s about safety. And safety is nonnegotiable.

Our bottom line is crystal clear: There can be no retreat from the extraordinary safety record U.S. aviation has achieved, and 5G is not ready for takeoff.

5G Best Practices in Canada

By contrast to what is unfolding in the United States, the government in Canada has also approved 5G in the C-Band but with restrictions against use in the vicinity of 26 airports and other measures to ensure aviation safety. They continue to monitor the situation and may impose additional restrictions as more data becomes available. ALPA supports these actions and is working alongside other aviation and wireless colleagues to ensure safety of airline operations while 5G C-Band deployment continues.