On Jan. 19, telecom companies finally began switching on their new “C-band” 5G cell networks. Built for billions of dollars over the last two years, the new wireless standard promises to deliver download speeds 10 times faster than old 4G networks to smartphone users across the US.
But the rollout of C-band networks has been anything but smooth for the aviation industry.
Airlines canceled at least 275 flights and delayed over 1,000 more on Jan. 19 amid fears that the new 5G networks would interfere with crucial airplane instruments and raise the risk of crashes. A voluntary decision by AT&T and Verizon to delay deployment of about 10% of its 5G cellular antennas around airports prevented the chaos that airlines predicted would make the “nation’s commerce grind to a halt,” but the confusion has prompted angry recriminations between cell carriers and airlines.
“This is one of the most delinquent, utterly irresponsible issues… I’ve seen in my aviation career,” the president of Emirates airline Tim Clark told CNN. A spokesperson for AT&T added the company was “frustrated by the FAA’s inability to do what nearly 40 countries have done, which is to safely deploy 5G technology without disrupting aviation services, and we urge it do so in a timely manner.”
The US Federal Aviation Administration (FAA) is now scrambling to test and approve airplane equipment to fly near 5G towers after US regulators dragged their feet for nearly two years.
The FAA has already determined that 62% of US commercial airplanes should have no problems with 5G towers, and said it expects to clear even more plane models in the coming days. But it has issued warnings that some planes, like the Boeing 787, should take extra precautions when landing in wet or snowy conditions because of the potential for C-band 5G signals to interfere with their radar altimeters.
The worry is that C-band 5G towers, which operate in a frequency range between 3.7 and 3.98 gigahertz (GHz), may interfere with airplane altimeters, which operate in a neighboring frequency range between 4.2 and 4.4 GHz.
Altimeters are key instruments that measure an airplane’s distance from the ground and affect the function of other safety and navigation equipment. A malfunctioning altimeter would pose a safety hazard for any pilot taking off or landing in bad weather, when airplane crews rely heavily on their instruments to navigate.
The FAA and airlines have been warning about the potential for C-band 5G networks to interfere with airplane altimeters since 2015. In 2018, Boeing and the US Air Line Pilots Association raised concerns over 5G to the US Federal Communications Commission (FCC), and the UN’s International Civil Aviation Organization recommended that countries should only deploy C-band networks after testing their impact on airplane altimeters.
The issue was on the US government’s radar. Before the FCC gave wireless carriers permission to use the C-band frequency range in 2020, it considered tests of C-band 5G networks’ impact on airplane altimeters. In February 2020, the FCC had auctioned off the C-band frequencies to AT&T and Verizon for $70 billion. In a February 2020 regulatory ruling, the FCC wrote that “the limits we set for the 3.7 GHz Service are sufficient to protect aeronautical services in the 4.2-4.4 GHz band.”
Over the next 21 months, regulators did little as AT&T and Verizon spent billions of dollars to build out their C-band networks. But in November 2021—two months before C-band 5G was due to be rolled out—the FAA finally sent a letter (pdf) to airlines, airplane manufacturers, and altimeter manufacturers asking them to test 5G towers’ impact on specific altimeter models and submit their data to the FAA. By December, the FAA still hadn’t issued regulatory approvals for specific altimeter models. It then asked wireless carriers to delay the 5G rollout for two weeks, until Jan. 19, to give regulators more time to figure out which altimeters might be affected.
Wireless carriers were annoyed, but agreed to delay the 5G rollout and carve out 5G exclusion zones around 50 major airports. “We were told for the first time late last year that the [FAA] and parts of the aviation community had concerns about the timing of our use of C-Band under the FCC’s February 2020 order,” the CEOs of AT&T and Verizon wrote in a Jan. 2 letter to the FAA. “Now, on the evening of New Year’s Eve, just five days before the C-Band spectrum will be deployed, we received your letter asking us to…once again assist the aviation industry and the FAA after failing to resolve issues[.]”
The FAA says it used that two-week reprieve to, among other things, facilitate “data sharing between avionics manufacturers and wireless companies.” But by its self-imposed Jan. 19 deadline, the FAA had only verified that five altimeters used in 62% of the US commercial air fleet won’t be impacted by C-band 5G signals. It’s still working on issuing regulatory approvals for additional altimeter and plane models.
Wireless carriers point out that 40 other countries have already deployed some version of C-band 5G without interfering with aviation instruments. But the FAA says that US 5G networks are slightly different from the networks in other countries, and argues that it holds itself to a higher safety standard that requires extra caution with new technologies like 5G. (The regulatory body may also be erring on the side of caution in the wake of the Boeing 737-Max crashes, which exposed lax FAA oversight.)
“Recent dialogue has helped to establish information sharing between aviation and telecommunications sectors and newly agreed measures to reduce the risk of disruption, but these issues are ongoing and will not be resolved overnight,” the FAA wrote on its 5G information page.
Over the coming weeks, AT&T and Verizon will likely finish rolling out their C-band 5G networks in hundreds of cities across the US, if a little behind schedule. While US air passengers won’t face additional safety risks, their flights may be canceled or delayed if the altimeter model used in their particular airplane hasn’t yet been cleared by the FAA. The agency has not released a deadline to issue those approvals, but said it expects to issue “more approvals in the coming days.”