5G and Aviation – The Spectrum Conflict Cools

Tony:

Hello, today is Monday, October 27^th 2025, I’m Tony Mangino from TC2 and this is Staying Connected.

In previous episodes of Staying Connected, we discussed the technological and regulatory struggle between the aviation industry and the wireless communications industry over the use of the lower C-band. Today we discuss how that tussle has taken a cooperative turn in the upper C-band. Joining me today for this discussion is Steve Rosen, a partner at LB3 whose practice includes, among other things, FCC regulation of wireless services. Welcome back to Staying Connected, Steve.

Steve: Thanks, Tony. Good to be back.

Tony: So Steve, the topic for today’s podcast sounds familiar. Didn’t we just record a series of podcasts on the lower C-band and the conflicts between the aviation industry and the wireless industry over its uses? And, what is the difference between the lower C-Band and the upper C-Band.

Steve: Your memory is good Tony.  We have discussed at some length the conflicts between aviation and 5G over the lower C-Band, which is located from 3.7 to 3.98 GHz. Today we are talking about the same regulatory and technological conflicts, but this time as they relate to the upper C-Band, which is located at 3.98 to 4.2 GHz.

Tony: Got it. But before we talk about the upper C-Band, can you give us a brief rundown on what happened with the lower C-Band?

Steve: Absolutely. Here’s a thumbnail sketch. During the 2020 FCC rulemaking that established the spectrum allocation and service rules for the lower C-Band, the aviation industry and the wireless industry clashed openly over the service rules placing limits on power and out of band emissions. The 5G community, including wireless carriers and wireless equipment manufacturers, favored higher power and less limitations on out of band emissions. The aviation industry, including aircraft manufacturers, airlines, and aircraft equipment manufacturers favored lower power and more stringent out of band emission limitations.

Tony: Why the difference of opinion?

Steve: Good question, Tony. The wireless industry favors higher power because higher power results in a stronger signal, which, all other things being equal, means better cellular coverage. And, because out of band emissions—which tend to increase as power increases—do not interfere with cellular handsets, the wireless industry is less concerned about limiting these emissions. The aviation industry is in an entirely different position because an important aircraft safety system, the radio altimeter, operates at 4.2 to 4.4 GHz. Given the proximity of this frequency band to the 3.7 to 3.98 GHz lower C-Band, increased power and out of band emissions from the lower C-Band are likely to interfere with radio altimeters.

Tony: And interference with radio altimeters is not desirable because radio altimeters are an important part of an aircraft’s safety systems that tell the pilot and autopilot how far the aircraft is from the ground?

Steve: Correct. Radio altimeters are critical in preventing aircraft accidents.

Tony: So how did the FCC resolve these competing claims?

Steve: In its 2020 C-Band Order, the Commission recognized the aviation industry’s interference concerns but sided with the wireless industry and promulgated the higher power and out of band emission limitations it sought. The Commission then urged the aviation industry and the 5G industry to collaborate if these interference concerns materialized.

Tony: I sense foreshadowing. Did the 5G-radio altimeter interference ever materialize?

Steve: Your sense is good. Fast forward to the late 2021 go-live date of the lower C-Band 5G licensees—AT&T, TMo, and Verizon Wireless—and there is trouble in the air. Or, more accurately, the National Airspace System.

Tony: Close it all down as a safety measure?

Steve: Precisely. The FAA, unlike the FCC, took the radio altimeter interference claims quite seriously. And while the FAA (unlike the FCC) had no power to delay the go-live date of the 5G transmitters, it did have the power to close the NAS. Which it threatened to do if its interference concerns were not addressed.

Tony: And that got everyone’s attention?

Steve: It did. President Biden’s Counsel of Economic Advisors set the wheels in motion to convene the muti-stakeholder meeting that had been suggested by the FCC in its C-Band Order. In early 2022, the wireless industry, the aviation industry, the FCC, and the FAA collectively agreed to a number of interference mitigation strategies that allowed the 5G licensees to go-live and the NAS to remain open. These mitigations included the lower C-Band licensees reducing transmitter power, especially near airports, and the aviation industry retrofitting commercial aircraft with interference resistant radio altimeters.  By September 2023, the entire U.S. airline fleet had upgraded their equipment and the risk of 5G interference has been substantially mitigated.

Tony: Got it—so the 5G licensees and the aviation industry are now successfully sharing the lower C-Band.  But what’s going on with the upper C-Band?

Steve: It’s the same but different! There are the same if not greater interference concerns because the upper C-Band is even closer to the radio altimeter’s operating frequency.  But it is different because the FCC, FAA, wireless industry, and aviation industry are now alert for the need to coordinate equipment rollout and specifications prior to upper C-Band go-live.

Tony: What are all of those stakeholders doing to prevent a repeat of the lower C-Band difficulties?

Steve: This time they are much better at acknowledging the potential for C-Band interference with radio altimeters and taking proactive measures to mitigate that interference. Rather than moving straight to a notice of proposed rulemaking, in February the FCC issued a notice of inquiry for the upper C-Band to, among other topics, elicit information on the potential for interference with radio altimeters. Encouragingly, the major trade associations for the wireless industry, the airlines, and the aircraft and radio altimeter manufacturers have filed a series of pleadings in this proceeding in which they enumerated the concrete steps that they are taking to ensure 5G/radio altimeter compatibility, including monthly technical working sessions to set equipment standards.

Tony: That does sound like more coordinated, collaborative process. But it’s never that simple in practice—where do you see bumps in the road?

Steve: Yes Tony, when these two huge segments of our economy try to share a spectrum resource equitably, pressure points will arise. The narrow guard band between the proposed 5G allocation and the radio altimeter band will present a technical challenge. And,  the comparatively long development cycle for the next generation of interference-resistant radio altimeters as compared to wireless telecom equipment will present a standards setting and manufacturing challenge. Finally, the question of  who will pay for any needed radio altimeter retrofits will be a test of political clout.

Tony: Thanks for the update today Steve, always a pleasure to have you on the program!  And to our listeners, if you’d  like to learn more about how the conflict between the aviation industry and 5G providers might impact your business or if you’d like to discuss other ICT needs with Steve or me, or any of our LB3 and TC2 colleagues, please give us a call or shoot us an email.

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