Despite a last-minute compromise with Verizon and AT&T brokered by the federal government that will at least temporarily limit deployment of 5G cell service around airports, limitations on airplane operations at Seattle-Tacoma International Airport still took effect at 9 p.m. Tuesday.

Thanks only to the reasonably clear weather, significant flight cancellations are not anticipated at Sea-Tac on Wednesday, said Bret Peyton, Alaska Airlines director of flight operations engineering and fleet technology.

Update: FAA clears 62% of U.S. fleet to operate at airports with 5G

But in a chaotic rollout of the new 5G network service, Federal Aviation Administration flight restrictions remain in place that will stop many airplanes from landing at Sea-Tac if the weather deteriorates so that the cloud ceiling is below 200 feet.

And Boeing has issued instructions to airlines about flight restrictions on its airplanes that have caused some foreign airlines to stop flying 777s into the U.S.


The FAA is conducting an airport-by-airport and airplane-by-airplane analysis of the risk of interference between the cell signals and airplane systems. Airlines are hoping the FAA can complete within days a Sea-Tac-specific risk analysis that will allow those limits to lift.

Otherwise, Peyton said, widespread flight cancellations and air travel chaos are inevitable here as soon as the weather reverts to its seasonal norm.

Peyton said in an interview Tuesday that the airline won’t take risks and must abide by the FAA limitations.

“If this would have happened Saturday, Jan. 15, we basically wouldn’t have landed an airplane in Seattle,” Peyton said. “No airline would.”

He said 99% of flight operations at Sea-Tac on Saturday were conducted in weather conditions that would have restricted most flights from coming in to land.

His team estimates that under the restrictions, if fog descends on Sea-Tac until 10 a.m. some morning, Alaska will have to cancel 126 flights in and out of the airport, affecting 13,000 passengers. And if fog returned in the evening, another 144 flights would have to be canceled, affecting a further 14,000 passengers.


The Port of Seattle estimates that the cloud ceiling at Sea-Tac is below the trigger point about 20% of the year.

“For tonight, we’re restricted just like the deal didn’t happen,” Peyton said. “And we have to be that way until the FAA gives us official notice that it’s safe and everything’s been looked at.”

Delta said Tuesday evening it is planning for the possibility of weather-related cancellations caused by the 5G deployment at dozens of U.S. airports, starting Wednesday. 

Boeing on Monday sent messages to airlines with guidance that because of the 5G restrictions taking effect, those flying the widebody 777 and 747-8s should not land at U.S. airports.

The guidance also told airlines flying the 737 MAX that a takeoff and landing performance penalty will apply that will require them to reduce either cargo or passenger weight on the aircraft.

Airlines worldwide rush to change flights over U.S. 5G dispute

International carriers Emirates, Air India, All Nippon Airways and Japan Airlines all canceled some flights to some U.S. cities Tuesday or switched out a 777 for a 787.

Neither Boeing nor Airbus nor the FAA commented publicly Tuesday.

Interfering with critical altitude readings

As reflected in competing multimillion-dollar ad campaigns from the two telecom giants that have bombarded TV viewers, Verizon and AT&T have been heavily marketing their introduction of fast 5G broadband service starting at midnight Eastern time Wednesday.

Months of standoff and political drama in Washington, D.C., saw the aviation industry try to delay the deployment around airports for fear of potential signal interference with airplane avionics as jets take off or land.

Telecom companies paid $81 billion at a government auction last year to secure a specific part of the wireless spectrum for their 5G networks. The aviation industry had warned as early as 2018 that this part of the spectrum is close to the frequencies used by some airplane systems.

Specifically, the 5G signals have the potential to interfere with an instrument called the radio altimeter, which tells the pilots how high a plane is above the ground or water. It’s a critical reading when a plane is taking off or landing.

In more modern jets, that altitude reading is fed into other systems, that can also be affected. On Boeing’s 787, for example, the altimeter reading is used to determine the timing and power of the automatic braking systems upon landing.


Peyton said that because of such integrated systems, more modern jets like the 787 and the 737 MAX are likely at greater risk from the 5G cell network interference.

He said the weight penalty guidance Boeing issued for the MAX under the 5G restrictions “tends to be small … unless there’s snow and slush on the runway.”

“We’re fortunate at Alaska that we don’t fly the MAX to too many affected cities where that runway condition would be onerous for us,” he added. “But that’s something we have to keep an eye on now.”

Earlier in the day, Verizon and AT&T each bowed to pressure from the White House and Congress and announced a decision to limit 5G network deployment around airports.

AT&T said it will “temporarily defer turning on a limited number of towers around certain airport runways” while it continues to work with the FAA and the aviation industry.

Details on which towers and for how long were not provided.


To assess the risk to airplanes, the FAA is analyzing the potential 5G interference on the three standard radio altimeters used on airliners — made by Collins, Honeywell and Thales. Each one reacts differently.

The Collins radio altimeter, which is the one on the bulk of Alaska’s fleet, has already been cleared at some airports. The Honeywell altimeter, installed on Alaska’s fleet of Airbus jets, has not.

The altimeters on the Bombardier Q400 and Embraer E175 regional jets flown by sister carrier Horizon Air are different than those on the Airbus and Boeing jets.

However, application of the restrictions depends on more than the specific model of altimeter. They are imposed airport by airport, depending on the positioning of cell towers around the runway. And they vary aircraft by aircraft depending on how the altimeter is integrated with other systems.

Peyton said Alaska Airlines has to wait for the FAA to finish its work.

“It’ll spin at the speed they can safely analyze everything,” he said. “That analysis takes a little while to grind through the work.”

President Joe Biden issued a statement Tuesday welcoming the Verizon and AT&T agreement and saying it “will avoid potentially devastating disruptions to passenger travel.”

It may do so, but the clock is till ticking for the FAA to close the deal, airport by airport and airline fleet by airline fleet.