Hidden Content
Is the government boosting 5G by selling bandwidth that could knock out altimeters? The FAA is concerned.
The FCC says it's left enough of a buffer, but an aviation industry study says otherwise.
Who's right? That's not clear yet, but aviation groups are asking for more time to explore it.
In the long march toward 5G cellular networks, we’ve seen it all: wild conspiracy theories, true stories of weather reading interference, and the perplexing idea that the Federal Communications Commission (FCC) can “sell” areas of bandwidth to the highest bidder.

Now, the U.S. military is expressing concern that the auctioned bandwidth is overly close to the frequencies used for air navigation; several commercial aviation groups say the sale could lead to “catastrophic failures” and “multiple fatalities,” according to a new report in Defense News. Even the Federal Aviation Administration (FAA) and Department of Transportation have asked the FCC to stop while they investigate the concerns.
What’s the deal with 5G, and why is it so fraught? Some of that is totally normal, because making room in both the technological landscape and the public imagination for a whole new data infrastructure is a big deal.
It’s hard to get people to buy into a change, even if it will eventually be good—and so far, it’s not persuasively clear to many that 5G is good.
That’s not just the conspiracy theories, which are thoroughly and ongoingly debunked, but simply questions of the cost of change versus the lower cost of staying the same.

And the sale of bandwidth is a big part of the cost of change, it turns out. The issue right now is the auctioned bandwidths are crowding out a key piece of aviation hardware, and not only for the military. That's just an example of a group with the most to lose, like the similar situation with weather satellites that measure water vapor noise in some nearby 5G bandwidths.
“This particular auction involves spectrum in the 3.7–3.98 GHz frequency, with the hope of selling more than 5,000 new flexible-use overlay licenses. Currently, the 3.7–3.98 GHz frequency portion of the C-Band is relatively quiet, occupied predominantly by low-powered satellites. For decades, this made the neighboring 4.2-4.4 GHz frequency a perfect place for the operation of radar altimeters, which are also called radio altimeters.”
Think of “bandwidth pollution” like light pollution—you might be 50 miles from the big city, but that’s still close enough to ruin your view of the night sky. In this case, altimeters measure how close planes are to the ground, most importantly in the low altitudes where their other instruments don’t work. Defense News continues:

“Once 5G telecommunications are introduced in the 3.7-3.98 portion of the band, there is a ‘major risk’ that those systems will create ‘harmful interference’ to radar altimeters, according to an October study from the RTCA, a trade organization that works with the FAA to develop safety standards.”
In its defense, the FCC says the buffer of bandwidth is large enough that it doesn’t believe altimeter interference is even a real possibility.
But the concerns are being pushed by a telecommunications lobbying group, and the FCC itself is led by partisan former Verizon lawyer Ajit Pai, who also opposes net neutrality.

The aviation industry, including private, commercial, and military groups, is asking for a pause in progress while it investigates the possibility of interference.