During the past year, the wireless and aviation industries have squared off over whether next-generation 5G services to be deployed in a swath of spectrum known as the “C-Band” could cause interference to radio altimeters on aircraft (altimeters measure altitude, a critical function of aviation safety when landing).  Earlier in 2021, the Federal Communications Commission (FCC) auctioned the C-Band spectrum for a record $81 billion after a full multi-year evaluation of the interference claims and set a December 5, 2021 launch date.  At the last minute, the Federal Aviation Administration (FAA) jumped into the fray, triggering delay and uncertainty. 

Just a month before major auction winners AT&T and Verizon were set to roll out C-Band 5G, the FAA issued a bulletin expressing concern and seeking data on altimeter operations.  In light of the ensuing uproar, AT&T and Verizon announced a temporary roll out delay until January 5, 2022 to continue discussions and then issued a series of temporary mitigation steps, even as they noted there is no reliable test data and no evidence of interference. 

Wireless providers in nearly 40 other countries operate 5G networks on C-Band spectrum, and planes—including U.S. airliners—land safely every day in those countries, with no evidence whatsoever of harmful interference to altimeters.  Regarding these international deployments, the FAA even acknowledges in its November Bulletin “[t]here have not yet been proven reports of harmful interference due to wireless broadband operations internationally” even while it continues to sound the alarm.  The FAA has now directed pilots to take measures that avoid reliance on altimeters when landing planes at airports near C-Band 5G base stations.  Pilots would be alerted to the presence of such possibly interfering signals through FAA-issued “NOTAM’s” – or Notice to Airmen.  

This is, as they say, no way to run a railroad or to manage the friendly skies – and it is no way to oversee America’s use of valuable spectrum resources, especially in a band that is harmonized internationally for 5G.

First, the FAA’s actions are based on a single aviation industry stakeholder study which relies on questionable assumptions.  The wireless industry has emphasized its shortcomings since its release.  Aviation stakeholders withheld the underlying test data from public view for nearly a year and a half, and its release just last month only underscores that the engineering behind the interference claims is suspect.  The FAA cites to the aviation industry report and states “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.”  That after-the-fact standard—steeped in proving a negative—reverses spectrum management policy and threatens to put a stop to spectrum development.

Second, the federal government has two expert agencies charged with the spectrum management portfolio, and the FAA is not one of them.  The FCC oversees commercial, state, and local (mainly public safety) use; the Commerce Department’s National Telecommunications and Information Administration (NTIA) manages federal spectrum use.  Both agencies are charged with protecting spectrum users from harmful interference.  The FCC provides notice of proposed technical rules, allows public comment, and with its spectrum engineers, transparently makes decisions in the public interest supported by the record.  The FCC only acted here after coordinating with NTIA and federal agency spectrum users including the FAA.  The FCC, when authorizing 5G in C-Band in early 2020, determined that 5G in the C-Band will be deployed in the 3.7-3.98 GHz range, with a spectral separation between 220 and 500 megahertz away from altimeters in the 4.2-4.4 GHz band.  This spectral separation, along with 5G transmitter limits, protects altimeters from any harmful interference.  Again, the United States is not an outlier here: experts around the world have determined that C-Band and radio altimeters can coexist safely, and real-world deployments confirm that.  For example, 5G is allowed all the way up to 4.0 GHz, with a guard band a 10th of the size the FCC provided.  After 17 years of global study, a multi-year FCC public rulemaking proceeding, and interagency dialogue across all relevant federal agencies, the FCC determined that mobile broadband in the C-Band spectrum would not cause harmful interference to aircraft operations.  The FAA is not tasked with spectrum management and the agencies so tasked did the appropriate due diligence, including by NTIA already coordinating with the FAA earlier in the process.

Third, reliance on federal rules properly adopted under the Administrative Procedure Act is a cornerstone of our national economic system and allows companies to invest and innovate with confidence.  The time for the FAA to have raised concerns regarding possible interference to altimeters was before the FCC adopted its 5G C-Band rules in February 2020 and certainly before America's 5G providers paid over $80 Billion to the U.S. Treasury—in the most successful auction in FCC history.  The FAA’s actions—last-minute, without basis, and flying in the face of real-world experience in nearly 40 countries—undermine investment-back expectations in the United States and curb U.S. leadership in 5G

Allowing any sector or agency unhappy with an FCC determination to create a “delay of game” to re-litigate their concerns is untenable This is particularly true when the technical arguments that objectors are making are substantially in dispute.  Second guessing the FCC’s determination now undermines our economy and our hard won global lead on 5G.  On December 22, the mobile and aviation industries put out a joint statement that they would work “together to share the available data from all parties to identify the specific areas of concern for aviation.  The best technical experts from across both industries will be working collectively to identify a path forward, in coordination with the FAA and FCC.” The Biden Administration needs to leverage this cooperation, clean up this bureaucratic mess, and clear the way for needed 5G growth.         


Note from the Editor: The Federalist Society takes no positions on particular legal and public policy matters. Any expressions of opinion are those of the author. We welcome responses to the views presented here. To join the debate, please email us at [email protected].