American telcos Verizon and AT&T were on the verge of firing up antennas to offer 5G wireless service this week, but held off on activating transmitters near airports when airlines said the signals from the antennas could disrupt their planes’ instruments.

The U.S. Federal Aviation Administration (FAA) warned that “because the proposed 5G deployment involves a new combination of power levels, frequencies, proximity to flight operations, and other factors, the FAA will need to impose restrictions on flight operations using certain types of radar altimeter equipment close to antennas in 5G networks.”

Why is the U.S. going nuts about it?

In the U.S., 5G service uses slices of radio spectrum as high as 3980 MHz. Plane altimeters use a band between 4200 MHz and 4400 MHz to bounce signals off the ground to check their heights. The fear is that those signals are close enough to interfere and potentially imperil landings, especially in bad weather.

The Federal Communications Commission’s Brendan Carr (a Republican appointee) condemned “a failure of competent leadership” and said the FCC is the proper authority, it carefully studied the issue, and the 5G broadcasts would be safe.

Industry observers are dismayed.

The FAA is now testing a variety of altimeters to make sure they’re safe from interference.

Why isn’t Canada’s air industry going nuts?

Canada’s existing 5G services operate at lower frequencies than in the United States—the closest are centred on 3500 MHz instead of 3800 MHz. Also, in a move that startled telcos last fall, the federal government told them to turn down the power on 5G antennas near airports and point all of them down, away from air traffic.

“I don’t think the FCC has passed any mitigation measures,” said David Farnes, general manager of the Radio Advisory Board of Canada, a specialized federal body that helps the government with technical radio-spectrum issues.

The order to angle 5G antennas toward the ground means even aircraft making odd landings—medevac helicopters, for instance—would be protected, Farnes told The Logic.

…Should we be going nuts?

Canada’s next spectrum auction is for the 3800-MHz band and the government is currently consulting on the terms. Farnes pointed out the first question in the Innovation Department’s survey asks about measures to keep those signals from interfering with aviation. Both that department and Transport Canada are in a working group monitoring and assessing the problem, he added, and are cooperating.