What You Need to Know About 5G and Air Travel Safety Concerns

But what led to this panic? What’s being done to address it? Let’s look at the facts so you understand what impacts—if any—the 5G C-band will have on air travel.

What is C-Band?

Last year, we first wrote about the C-band range of spectrum. It became commercially available through a Federal Communications Commission (FCC) auction that ended in January 2021.

Many future applications call for spectrum that falls somewhere between the high- and low-frequency bands … and that’s where C-band comes into play. Sometimes referred to as “mid-band,” you can think of C-band as the “Goldilocks” of frequency: not too low and not too high. It provides a solid mix of coverage and capacity.

As some mobile carriers were getting ready to activate C-band signals on Jan. 19, 2022, as planned, the airline industry stepped forward to voice concerns about potential 5G signal interference with radio altimeters (instrumentation used by pilots to safely operate commercial flights).

It’s true: C-band spectrum is close to the spectrum used by radio altimeters (also called “radar altimeters”). Some radio altimeters—especially older models—may be able to pick up noise from these adjacent frequency bands, which could impact landing in poor-visibility conditions (rain, snow, fog, etc.). The concern was that interference from 5G signals could result in incorrect—or loss of—radar altitude information.

What Led to the Sudden Panic?

In a February 2020 Report and Order approving use of the C-band for wireless service, the FCC concluded that “well-designed [radio altimeter] equipment should not ordinarily receive any significant interference (let alone harmful interference) given these circumstances.”

In October 2020, the Radio Technical Commission for Aeronautics (RTCA) released a study outlining potential interference impact on radio altimeters.

Then, in December 2021, the Federal Aviation Administration (FAA) released SAIB AIR-21-18, a bulletin that acknowledged these concerns about impacts on radio altimeters, announced the continued deployment of 5G and encouraged manufacturers, operators and pilots to make sure altimeters will continue to function by conducting adequate testing and ensuring proper qualifications.

It was this FAA statement that caught the attention of airlines and motivated the industry to take action by cancelling flights out of an abundance of caution.

Why Did This Happen in the United States?

Why wasn’t this a concern in other countries? Why did it happen only in the United States?

First, it’s important to note: Because planes fly internationally, the frequency bands used by radio altimeters are universal. Bands used for other purposes aren’t universal and do not apply internationally.

In parts of the world that aren’t governed by the FCC, countries have their own regional frequency bands. These are different than the United States’ frequency bands—and happen to be slightly to the left of the bands used by radio altimeters.

For example, in the United States, C-band uses the 3.7 GHz to 3.98 GHz spectrum. In Europe, however, it uses the 3.4 GHz to 3.8 GHz spectrum. As these numbers reveal, the U.S. C-band spectrum is closer than the European C-band spectrum to the band used by radio altimeters (4.2 GHz to 4.4 GHz).

Because frequency signals aren’t exact rectangles, some separation is needed between licensed bands to create a layer of protection that prevents signal interference. Other countries have more of a guard band or “cushion” between the two spectrums.

Another interesting note: Some countries took extra precautions and worked closely with the European Aviation Safety Agency and the European Communications Commission to make sure the towers that surround airports are low and have antennas that point away from runways—creating a safety bubble.

Is the Issue Being Addressed?

The bottom line: 5G signal interference impact on radio altimeters was a very remote possibility. C-band frequency was used in the past for point-to-point satellite communications without any problems. But, in the spirit of being safe—and because 5G is point-to-multipoint communication—all involved parties are doing whatever they can to create a sufficient buffer between the spectrums used by 5G and radio altimeters.

Ongoing testing, approval of appropriate radio altimeters and the creation of airport safety bubbles seen in other countries are all being carried out in the United Sates.

We applaud the mobile carriers’ decision to work with the Executive Office of the President to conduct a thorough analysis of conditions and ensure safety and proper performance.

Progress continues to be made (you can see the latest updates here): Currently, 90% of aircraft has been cleared, and work is continuing to define 5G areas around airports.

If you have any questions about 5G or C-band deployment, send me a note. I’ll share the latest information I have.