DALLAS – Concerns about the potential impact of 5G on air traffic control communications led U.S. authorities to request a second delay in its national rollout.

While the next generation of cellular network technology provides significant benefits for consumers and businesses, certain frequencies that it uses may interfere with some radio devices — like the radio altimeters pilots rely on.

Now, the Federal Aviation Administration (FAA) is locked in a standoff with two major U.S. wireless carriers. A temporary hold on 5G’s rollout will prevent flight delays in early January, but it’s possible a new FAA rule could delay flights later in the month.

Air traffic at Terminal 2. Photo: Frankfurt Airport

5G Operating Frequencies Could Interfere With Air Traffic

In early December 2021, it became clear to the FAA that the rollout of a new 5G frequency band by AT&T and Verizon — the mid-spectrum 3.7 to 3.98 GHz “C-band” — could interfere with radio flight instrumentation.

Later that month, Transportation Secretary Pete Buttigieg sent a letter to the two carriers requesting a two-week delay of their rollout of C-band 5G.

If the carriers did not acquiesce, the FAA would implement a new policy limiting the use of radio altimeters and automatic landing sites at airports vulnerable to 5G interference. Thousands of U.S. planes will not be able to use automated and guided landing systems that typically support pilots in poor visibility conditions.

The administration had previously released a special airworthiness information bulletin on the potential for 5G to interfere with radio altimeters in November. The European Aviation Safety Agency issued a similar bulletin the following month.

FAA Air Traffic Control Tower. Photo: FAA Media

The Telecommunication Industry Responds to the FAA Rule

While AT&T and Verizon have taken steps that may reduce the impact of 5G on aviation safety, both carriers initially declined the FAA’s request for a two-week delay on the rollout of C-band 5G.

One day later, however, the two companies reversed course and agreed to Buttigieg’s requested two-week delay. The move will likely prevent serious delays at major airports around the country.

In addition to the delay, both AT&T and Verizon have agreed to take precautions that may help reduce the potential aviation impact of the new 5G frequency band.

In a letter to the Federal Communications Commission (FCC), sent in late November 2021, both carriers said they would implement power reductions on nationwide 5G towers that transmit over the C-band spectrum. These power reductions will be in place for six months.

The two carriers, along with experts from the FCC, say they do not anticipate the new spectrum to have a major impact on airline instrumentation. However, they will implement power limitations while the FAA studies the issue.

Photo: JFK

How Would the FAA Rule Have Impacted Flights?

The FAA rule on 5G was set to go into effect on January 5, 2022, the same day that AT&T and Verizon originally planned to begin their rollout of C-band 5G operations. The implementation of the rule at airports around the country would have likely meant flight delays. Flights to certain airports where visibility was low could have been delayed or diverted while the FAA rule was in place.

Pilots who could prove their airplanes are equipped with altimeters that would not be impacted by 5G interference could have been exempted from the rule. However, most pilots would likely have been subject to the rule — and would have faced the significant potential for flight delays as a result.

The impact of the rule would likely be felt the most in cities where the 5G rollout was already well underway, and where new 5G base stations were already in place.

The 5G rollout had already been completed in most major American cities, meaning large airports — like Atlanta, Los Angeles, New York City, and Chicago — were most likely to face significant delays due to the FAA rule.

While the rule isn’t likely to go into effect on January 5, 2022, it’s still possible that a similar rule may come later.

If the FAA finds that C-Band 5G is likely to interfere with radio instrumentation and the two major 5G carriers decline a request for a permanent delay, it’s possible the agency may once again consider telling pilots to avoid the use of radio altimeters.

FAA Air Traffic Control Tower. Photo: FAA Media

Aviation Experts Had Warned About the Potential for 5G Interference

In mid-2021, AT&T and Verizon acquired authorization for the 3.7 to 3.98 GHz band — also called the C-band spectrum — from the FCC. The acquisition, which cost around US$70bn, enabled the two carriers to offer mid-spectrum 5G coverage over wider areas than can be covered with high-band millimeter-wave 5G.

While the FAA rule is recent, major aviation organizations have been sounding the alarm about potential harmful interference from 5G since late 2020.

In November 2020, the International Air Transport Association (IATA) and International Federation of Air Line Pilots’ Associations (IFALPA) released a joint statement on the potential for interference, writing that “there is a major risk that 5G telecommunications systems in the 3.7 to 3.98 GHz band will cause harmful interference to radar altimeters on all types of civil aircraft.”

The two organizations wrote that interference to RA operations could cause a wide range of equipment failures, including issues with autoland functions, EICAS/ECAM, GWPS alerts, predictive wind-shear systems — which depend on altimeter readings to function properly — and other automatic flight systems.

5G 3.5 GHz cell site of Vodafone in Karlsruhe, Germany. Photo: By Tomás Freres – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=81025079

The Second Delay for the American 5G Rollout

The FAA request isn’t the first time U.S. officials have asked telecommunication companies to delay their rollout of 5G. In 2019, weather experts at NASA and NOAA voiced concerns that certain 5G frequency bands could interfere with important weather forecasting instrumentation.

According to these experts, one new 5G frequency band overlapped with the frequencies used by weather satellites to monitor and transfer data on water vapor.

5G tower transmissions could disrupt weather satellite communications, making it could more difficult (or even impossible) to accurately collect and transmit atmospheric water vapor data. Information on water vapor is key for accurate weather forecasting.

Despite these concerns, the FCC opted to auction those frequency ranges that had the potential to disrupt weather forecasting and weather satellite transmissions.

Now, more than two years later, experts continue to argue against the use of 5G and further 5G rollouts. In July 2021, the associate director of the National Center for Atmospheric Research testified before Congress that 5G transmissions were still likely to interfere with weather forecasting operations and said the loss of potential data could be “could be catastrophic for the nation.”

A7-BEE Qatar 777-300ER LAX Photo: Luca Flores/Airways

How Will C-Band 5G Impact Aviation?

On January 5, 2022, AT&T and Verizon did not begin their launch of C-Band 5G as planned — likely sparing a number of flights from delays due to visibility conditions.

Depending on FAA research, however, American pilots and airlines may face another crisis two weeks later. If the agency finds that 5G will disrupt radio instrumentation, it may implement a new policy limiting the use of automatic landing systems and radio altimeters at certain airports.

If the FAA chooses to reinstate the rule after further research, the impact could be significant, especially near major population centers where cell carriers have invested heavily in 5G infrastructure.

Featured image: Alexandr Podvalny via Pexels.com