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

Wireless Signals Could Interfere with Critical Flight Safety Systems

The 5G C-Band signals telecommunications companies activated on January 19, 2022, may interfere with equipment airline pilots use to safely operate commercial flights every day. Rolling out these signals without proper mitigations in place undermines flight safety and disrupts the entire aviation system.

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. Commercial aviation in the United States 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. If the C-Band transmissions launch on January 19 as planned, the Federal Aviation Administration (FAA) will issue—at a minimum—a restriction on low-visibility (poor weather) landings. These restrictions will ensure safety but will impact the aviation operations system and limit access to airports in low visibility conditions, causing flight delays, flight cancellations, and delayed package deliveries.

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.

In 2020, RTCA published a paper that evaluated the interference risk. That report has since been validated by the 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.

We have been warning these stakeholders since 2018 that the 5G plan would interfere with airplane radio altimeters, but they ignored us. Flight safety continues to be at risk. The reliability of air travel is at risk. Flight cancellations and operational disruptions could become the norm thanks to the FCC’s irresponsible actions—and the wireless industry’s decision to broadcast with little regard to the impact on aviation. We all want 5G, but not at the expense of aviation safety and hundreds of thousands of flight cancelations. For pilots, this isn’t about politics or profit, it’s about safety. And safety is non-negotiable.

What’s Happening Now

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 are asked to report radio altimeter anomalies to their airlines and to ALPA through our DART system

We are still hopeful that the wireless industry will collaborate with the broader aviation community on effective solutions that will ensure that every passenger and cargo flight arrives safely without severe operational disruptions.

ALPA’s Recommendations

Collaboration between the telecommunications and aviation industries and the government to identify risks and implement mitigation strategies, such as:

  • 5G C-Band best practices used around the world—including Canada and France—such as restricting the subset of problematic 5G signals from being transmitted near airports.
  • Allow 5G at reduced transmitting power, instead of test driving it on the U.S. power system.
  • Utilize other techniques, such as pointing antennas below the horizon to ensure that radio altimeters do not experience interference.

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.