Though the aviation and wireless industries now agree that wireless signals won't affect aircraft safety, the agencies spent years arguing the point.
A public spat between two federal agencies spiraled out of control earlier this month when airlines started canceling flights into US airports amid safety concerns about the effects of 5G wireless signals on airplane equipment.
Though the quarrel between the Federal Communications Commission and Federal Aviation Administration centers on a relatively new technology, it has roots that go back more than a decade. For years, the FAA and the aviation industry have questioned whether 5G signals in a range of the wireless spectrum known as C-band could interfere with the altimeters in some commercial aircraft. Their fear is that any disruption to the altimeters, which pilots rely on during low-visibility landings to know how close they are to the ground, could lead to a crash.
But the Federal Communications Commission, which regulates the nation's airwaves, disagrees. Along with the wireless carriers, it says that it takes safety concerns seriously, and that years of analyzing the data shows no harmful interference between 5G signals and airplane equipment. There are worries that the studies FAA and the aviation industry have relied on are fundamentally flawed and don't represent real-world experience.
The clash between the two sides came to a head Jan. 16, just days before AT&T and Verizon were set to turn on their C-band 5G services, which fit into the wireless spectrum between the low-band and millimeter-wave 5G services already in use. Despite two delays and voluntary agreements from the wireless carriers to alter their deployment plans, the FAA began issuing warnings regarding the 5G interference near airports and airlines started canceling flights.
Since then, the two sides have largely settled their dispute. The FAA on Friday said the agency has come to an agreement with AT&T and Verizon on "steps that will enable more aircraft to safely use key airports while also enabling more towers to deploy 5G service."
While things have mostly calmed down, questions remain about how this last-minute scramble could have happened in the first place. The disagreement is also a foreboding example of how a dysfunctional federal process could be repeated and disrupt future wireless deployments or imperil other services that rely on wireless airwaves. This could spell bad news for consumers, as federal infighting could discourage innovations or harm existing services.
Brendan Carr, a Republican FCC commissioner, appointed under President Trump, said the concerns about 5G interference with aviation should have ended years ago when the FCC, which is designated by Congress to regulate airwaves, settled the safety questions in an open rulemaking. He said the FCC is well-equipped to handle interference concerns.
"The aviation industry participated in this process," Carr said in an interview. "But the result wasn't what they wanted. … We base our decisions on science and real-world experience, and we found there was no harmful interference."
But a former Department of Transportation official says the FCC was more concerned about boosting the fortunes of wireless carriers than about whether planes would crash. Diana Furchtgott-Roth, who was deputy assistant secretary for research and technology under Trump at the Transportation Department (of which the FAA is a branch), said that the FCC and the Commerce Department's National Telecommunications and Information Administration, which is tasked with advising the president on spectrum issues, didn't take the safety claims seriously.
She pointed to an FAA letter that detailed its concerns about 5G interference just before an auction of C-band airwaves took place in December 2020. She said the NTIA's decision not to forward the letter to the FCC, which runs spectrum auctions, was a deliberate attempt to suppress the safety issues. Instead, she said, her fellow Trump appointees were focused on pumping up the sale of the spectrum licenses in the upcoming auction.
"It's blindingly obvious; follow the money," she said in an interview. "Everyone was concerned about their 'legacy,' and they didn't want to risk depressing the sale price on an auction they expected to generate billions of dollars with a safety warning from another federal agency."
As it turned out, the auction exceeded everyone's expectations, bringing in over $80 billion to the US Treasury, making it the highest-grossing auction in the FCC's history.
Adam Candeub, a former NTIA chief, called Furchtgott-Roth's claims that the NTIA was trying to stifle the FAA "insane" and "ludicrous." He said the NTIA took the safety claims seriously, but determined "there was no there" to it. He added the agency was under no obligation to forward it to the FCC.
"The FAA is always free to go directly to the FCC, and many agencies do that when they disagree with NTIA," he said. "Our job is not meant to represent agencies before the FCC. We exercise our own independent scientific judgment."
But other former Commerce Department officials say that is isn't typically how the process works.
Regardless of how or where the breakdown occurred in 2020 during the Trump administration, Carr said the public feuding between the FAA and the wireless carriers, which is being brokered by the Biden administration, could have a chilling effect on investment in wireless spectrum. He said that allowing agencies like the FAA to go outside the congressionally mandated FCC process sets a precedent that will deter companies from investing billions of dollars in spectrum if they think that "after the fact, you may have to engage in some sort of backroom, behind closed door negotiation."
"It creates a lot of uncertainty in the market," he said. "We've now sent this signal to every agency that doesn't like the outcome of an FCC spectrum process that if you have a good enough public relations campaign, you can just hold on until the next administration and go directly to the White House, and maybe get a better deal."
To help you understand how this dispute evolved, we've put together this timeline.
Nov. 15, 2010
As a follow-up to the 2010 National Broadband Plan ordered by President Barack Obama, the NTIA issued its Fast Track evaluation report identifying various swaths of spectrum to be reallocated for broadband. The assessment included the C-band.
Aug. 3, 2017
The FCC began seeking comment on how to free up C-band (3.7GHz to 4.2GHz) spectrum for 5G.
Oct. 29, 2018
Aviation Spectrum Resources , which manages and coordinates radio communication licensing for the aviation industry in the US, confirmed in an FCC filing that it had been conducting tests since 2016 to broadly assess commercial altimeter performance.
July 13, 2018
The FCC issued a Notice of Proposed Rulemaking, which asked for comment specifically on wireless interference in the 3.7GHz to 4.2GHz band with altimeters. The FCC stated its intention to transition some or all of the band from satellite to terrestrial wireless broadband use.
Dec. 11, 2018
Aircraft maker Boeing filed comments with the FCC raising concerns over altimeters and 5G interference.
Oct. 22, 2019
The Aerospace Vehicle Systems Institute, a cooperative research group that is partially funded by the FAA, submitted to the FCC preliminary results of its 5G interference testing. It evaluated seven altimeter models whose identities were not disclosed. The report showed radar altimeter interference for 5G signals at the 3.7GHz band. It also showed one widely deployed altimeter performed significantly worse than most others, but didn't specify which one it was.
Nov. 18, 2019
FCC Chairman Ajit Pai announced plans to auction 280MHz of C-band spectrum. The agency also planned to relocate satellite providers that were already using the spectrum to deliver video programming to cable providers to another part of the band.
Feb. 28, 2020
FCC voted 3-2 to approve the plan to use C-band (3.7GHz to 3.98GHz) for commercial wireless service without any constraints on 5G deployments. The vote was split along party lines, with the three Republicans, Pai, Carr and Michael O'Rielly, voting in favor. Democrats Jessica Rosenworcel (now now the chair of the FCC) and Geoffrey Starks opposed the order. But the Democrats' opposition to the plan wasn't over interference concerns. Instead, they opposed the $10 billion payment the FCC planned to offer satellite companies to move to a different part of the spectrum block.
Throughout the process, the aviation industry had submitted comments. The FCC said that it evaluated that information and determined "the limits we set for the 3.9GHz service are sufficient to protect aeronautical services in the 4.2-4.4GHz band." It pointed to the 220 megahertz guard band that was put in place to protect altimeters.
The FCC encouraged the aviation industry and the wireless industry to convene a working group to continue to study interference between altimeters and 5G transmission in the C-band.
July 2, 2020
AVSI submitted another report, "Helicopter Air Ambulance RF Interference Scenario," to the FCC describing harmful interference in radar altimeters in helicopters.
June 2020 to October 2020
The C-band Multi-Stakeholder Group or TWG-3, which consisted of representatives from 29 companies and associations across the aviation industry, wireless industry and device manufacturers, was created to work out technical recommendations for how 5G and aviation could coexist. The group met several times over this period.
Nov. 13, 2020
The co-chairs of the TWG-3 working group, representing the Aerospace Industries Association and the wireless industry group CTIA , sent a letter to the FCC stating that after months of work, it was unable to come to consensus and would not submit any technical reports or recommendations to the FCC.
Oct. 7, 2020
RTCA published a technical report that concluded even with the 220MHz guard band, "5G operations in the 3.7-3.98 GHz band may create harmful interference to radio altimeters that would significantly degrade or completely interrupt their operation during critical phases of flight."
(The FCC and NTIA both said they reviewed this report, but found the data flawed and the conclusions overly conservative based on their analysis of real-world experience.)
Dec. 1, 2020
Steve Dickson, the administrator for the FAA, and Steven Bradbury, general counsel of the Department of Transportation under Trump, sent a letter to the NTIA's Candeub asking the NTIA to pass on a letter to the FCC asking for a delay in the C-band spectrum auction, scheduled to begin on Dec. 8.
The NTIA did not forward the letter, which acting head Candeub said the agency had reviewed, but he added that the NTIA was under no obligation to pass onto the FCC. The FAA and DOT did not send the letter themselves to the FCC.
Dec. 7, 2020
Rep. Peter DeFazio, a Democrat from Oregon who chaired the House Committee on Transportation and Infrastructure, sent a letter to Pai urging a delay until further study could be done to understand the full extent and severity of 5G interference. DeFazio acknowledged that the FCC left a 220-MHz guard band between the auctioned C-band spectrum and the aviation band, but pointed to the RTCA research showing that wasn't sufficient protection.
Dec. 8, 2020
Wireless carriers began bidding in the FCC's C-band auction. Experts predicted proceeds for the US Treasury from the auction of around $60 billion for the spectrum.
The FCC announced winning bidders in C-band auction. The record-setting auction was the largest in terms of revenue for the FCC, generating more than $81 billion. Verizon and AT&T spent a combined $70 billion on spectrum licenses.
March 25, 2021
During a hearing of the House Committee on Transportation and Infrastructure, Transportation Secretary Pete Buttigieg testified, answering a question about C-band interference, that "we are very concerned about the potential for harmful interference to radar altimeters." He added that the DOT would make safety the No. 1 priority.
Nov. 2, 2021
The FAA issued a special airworthiness information bulletin warning about 5G and altimeter interference.
Nov. 4, 2021
AT&T and Verizon agreed to delay their 5G rollouts using C-band spectrum for one month over FAA safety concerns.
Nov. 24, 2021
AT&T and Verizon agreed to 5G power limits for six months to resolve FAA safety concerns.
Dec. 16, 2021
United Airlines CEO Scott Kirby told reporters following a Senate Commerce Committee hearing that if AT&T and Verizon continued with their plans to begin using C-band spectrum for 5G service in January hundreds of thousands of passengers would face canceled and disrupted flights.
Dec. 31, 2021
Buttigieg and FAA Administrator Dickson sent a letter to the CEOs of AT&T and Verizon asking for a two-week delay to give the FAA more time to figure out which altimeters are affected.
Dec. 31, 2021
Airlines for America filed an emergency request with the Federal Communications Commission asking to further delay the rollout of new 5G wireless service near airports until further studies can prove the signals won't disrupt critical airplane instruments. The group, which represents 11 US passenger and cargo airlines including Delta, United, FedEx, UPS, Southwest and American, also threatened to sue the FCC if the agency didn't delay the 5G rollout.
The FCC didn't respond to the request, and Airlines for America didn't make good on its threat to file a federal lawsuit.
Jan. 2, 2022
AT&T and Verizon executives initially rejected Buttigieg's and the FAA's request. Instead of delaying the deployment, they offered to adopt the same C-band radio exclusion zones already in place in France near runways at certain airports.
Jan. 4, 2022
AT&T and Verizon caved to political pressure and agreed to the FAA's request for a two-week delay on 5G rollout. And they put in place 1.5-mile 5G exclusion zones at certain airports.
Jan. 5. 2022
Verizon and AT&T missed their planned 5G C-band network launch. The companies postponed those plans until Jan. 19.
Jan. 16, 2022
The FAA reported it had cleared only 45% of US commercial planes for low-visibility landings at many of the airports where 5G C-band would be deployed on Jan. 19.
Jan. 17, 2022
Executives from several major US airlines and cargo carriers wrote a letter to President Joe Biden warning of massive disruptions to travel and shipping unless the 5G rollout was delayed within a two-mile radius of airport runways.
Jan. 18, 2022
AT&T and Verizon once again caved to pressure, and they adjusted their 5G launch plans around airports as foreign airlines started canceling flights to the US.
Jan. 19, 2022
AT&T and Verizon launched the faster 5G networks, with exclusion zones in place around key airports.
Jan. 27, 2022
The FAA reported it had cleared 90% of US commercial planes for most low-visibility approaches at airports with 5G. But it continues to issue Airworthiness Directives for certain planes. The agency has been updating those directives almost daily.