Future Tense

The Showdown Over Airlines and 5G Is Part of a Much Bigger Problem

A plane flying by a cellular tower
Justin Sullivan/Getty Images

Which would you choose: far faster mobile broadband speeds and new services on your 5G-enabled smartphone or a greater risk that your next flight crashes on landing? This should be a false choice in tech-savvy America. Yet, according to the airlines and the Federal Aviation Administration, it is an unresolved risk.

Over the past few weeks, airline and FAA warnings about potential flight cancellations have spun up alarming headlines about the risk that the faster 5G mobile networks that Verizon and AT&T began activating last week will interfere with aircraft landing systems. United, Southwest, and other airlines threatened that if the two biggest mobile carriers turned their high-power transmitters on anywhere near airport runways, they would have to cancel hundreds of flights. “Chaos” would result, they said.

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None of this was necessary. The primary problem has been a steady breakdown in coordination and cooperation between the Federal Communications Commission, which regulates business use of increasingly crowded public airwaves, and the other federal agencies that rely on wireless frequencies or regulate a multitude of industries, like the airlines.

A quick (I promise) technical lesson: The airwaves, also called the “spectrum,” are the range of electromagnetic frequencies useful for transmitting and receiving radio signals. The spectrum is divided into blocks, or “bands,” of frequencies. To avoid interference, these bands are first allocated for a certain use (broadcast TV, aircraft altimeters) and then licensed either by the FCC for commercial use or by the Department of Commerce to federal agencies for government use (such as military radar and GPS). The FCC and the Department of Commerce’s National Telecommunications and Information Administration are expected to coordinate commercial and federal licenses and use.

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In a 2021 government auction, mobile carriers purchased “C-band” frequencies of the public airwaves for a record $81 billion. These bands lie close to the frequencies that aircraft altimeters use to measure the distance to the ground during landings. That technology, the FAA maintains, is especially critical for safe landings when the weather or other factors limit visibility. The airlines and FAA claim that 5G transmitters close to airports and operating at full power can cause some altimeters to malfunction.

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For its part, the mobile industry argues these fears are overblown and that this same spectrum is already in use for 5G in 40 countries without incident. It also emphasizes that unlike most neighboring services on the airwaves, there is a very wide (200 megahertz) “guard band” of frequencies used by satellites between the two services. When the FCC reallocated spectrum lower in the band for 5G mobile use, it explicitly determined there should be no adverse impact on altimeters. The mobile carriers have also argued that if older aircraft are using antiquated altimeters that are overly vulnerable to transmissions in neighboring frequency bands, it’s not their fault; the airlines have been on notice since 2019 that the FCC, like most of the world, was reallocating C-band for high-power mobile broadband.

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Late last week, the Biden White House scrambled to intervene, pushing the two industries—and the two warring federal regulatory agencies—into at least a temporary compromise: The mobile carriers agreed, among other mitigations, to larger buffer zones around airports where the new, faster 5G airwaves will not be used or will transmit at reduced power levels. Both sides agreed to continue working on a more permanent solution.

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Part of the problem is that neither the FAA nor the FCC required the airlines or the mobile companies to conduct real-world tests in advance to determine if and how 5G networks would actually disrupt altimeters and aircraft safety. But even if there were clear data, it’s likely that, like every other incumbent spectrum user, the airlines and FAA would adopt a parochial perspective and fight the slightest risk or cost imposed as the FCC unlocks new spectrum capacity for 5G, next generation Wi-Fi, and other new wireless technologies.

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The larger problem highlighted by the altimeter fiasco is the lack of an adequate national spectrum policy. Just as the world goes wireless—and the airwaves get more and more crowded—the coordination between the FCC and other federal agencies has broken down over the past five years. Unlike the Obama administration, which coordinated spectrum policy from the White House, the Trump administration had an ad hoc spectrum policy that failed to articulate a coherent set of national priorities that would supersede the natural NIMBY reflex of spectrum incumbents.

The FAA fiasco is just the latest in a series of standoffs over the past four years between the FCC and federal agencies defending the spectrum status quo. FCC proceedings to reallocate spectrum and assign frequencies to new uses take years—yet in too many cases, affected federal agencies do not actively engage in FCC rule-makings or contribute engineering data, but instead wait until after a final decision to raise alarms about potential calamity.

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Auto safety signaling: On Tuesday the U.S. Court of Appeals for the District of Columbia Circuit heard oral arguments in a challenge to an FCC decision brought by state and industry auto safety associations. The auto interests claim that Congress gave the U.S. Department of Transportation, and not the FCC, final say over how large a block of airwaves must be reserved for future vehicle-to-vehicle communication systems. The FCC set aside a large band for auto safety in 1999, but it has sat empty and idling ever since. In 2020, over the objections of then–Transportation Secretary Elaine Chou, the FCC unanimously voted to reallocate a portion of the band to enable faster new Wi-Fi technology. Tellingly, in an unusual move, the D.C. Circuit asked the Justice Department to address the significance of the fact that DOJ “is representing the FCC and not the Department of Transportation.” That’s a question the Biden White House could answer best by forcefully telling the DOT to back off and acknowledge that the FCC’s bipartisan decision is in the overall best interests of consumers and the economy.

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GPS: After a decade of debate, in 2020 the FCC gave Ligado, a mobile satellite company, the flexibility to repurpose a portion of the spectrum it has long licensed for 5G mobile and fixed broadband services. The rule-making had dragged on because of complaints from GPS users—including John Deere and other politically powerful sellers of equipment that relies on GPS—that the new, more intensive use could interfere with GPS that had assumed neighboring satellite bands would remain quiet at ground level indefinitely. After years of wrangling, private sector GPS users finally dropped opposition after Ligado agreed to give up a significant slice of its valuable spectrum (23 megahertz) as a guard band and to reduce transmit power levels by more than 99 percent of authorized levels. But after the FCC’s unanimous final order, the Pentagon stormed Capitol Hill demanding that the FCC reverse itself because important military GPS would need to be upgraded. While the FCC has stood its ground—and Ligado is preparing for commercial deployments—uncertainty remains, and it will be costly.

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Weather monitoring: Meteorologists use sensors on satellites to monitor various frequencies to collect data that help to predict weather patterns. One of those bands (at 23.8 gigahertz) is near a band the FCC auctioned in 2019. Although the FCC’s rule-making began in 2014, as with the FAA’s concerns about altimeters, it wasn’t until 2019 that the chief of the National Oceanic and Atmospheric Administration sounded the alarm, telling Congress that 5G mobile signals in the adjacent 24 GHz bands would endanger as much as 77 percent of the weather data collected by agency satellites. Then–FCC Chairman Ajit Pai and the mobile industry countered that NOAA’s objections were based on a “fake weather sensor” that was never deployed. Nevertheless, under congressional pressure, the FCC is likely to adopt additional protections for weather forecasting in line with international standards adopted subsequent to the FCC’s auction.

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So what is to be done?

First, the Biden White House needs to send a clear message that the Commerce Department’s

National Telecommunications and Information Administration is in charge of coordinating federal agency spectrum policy, just as Congress intended.

Second, the NTIA and FCC need to collaborate on an updated national spectrum policy and coordination process. President Barack Obama put the U.S. far ahead of the rest of the world by embracing the recommendations of the President’s Council of Advisors on Science and Technology in 2012 that federal and private sector spectrum sharing must become the “new normal” given the tsunami of wireless data and new technologies coming online in the years ahead. Unfortunately, while the FCC has pushed that approach forward, the executive branch has fallen back into paranoid parochialism.

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Third, the NTIA and any affected federal agencies need to participate actively in FCC rule-makings from beginning to end. They need to put up or shut up concerning interference concerns—and submit technical studies and data, just as private industry does.

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Fourth, the NTIA and the Department of Defense—by far the largest federal spectrum user—need to follow through rapidly on proposals to create an automated database to more efficiently coordinate spectrum sharing among agencies and with the private sector.

Finally, the White House needs to be what FCC Commissioner Brendan Carr recently called “the adult in the room.” Disputes that cannot be resolved through FCC and Commerce Department negotiation should be escalated for mediation. Whereas both the FCC and NTIA are to a significant degree “captured” by their role as advocates for the private sector and federal spectrum users, respectively, the right combination of officials in the White House should be in the best position to discern the overall national interest.

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.

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