The FAA is playing dirty.

After failing to win support from the administration and Congress for its unwarranted ban on deployment of mid-band 5G anywhere in the country, the agency is leaning on the firms it regulates to make its case. And they’re pressing the case by selective leaks to friendly media.

It’s like the Title II net neutrality war all over again, when former chairman Genachowski leaked a plan to impose Title II and Wheeler leaked a plan not to. Both leaks turned out to be false, of course.

Today’s Reuters Leak

Today the FAA (or an ally) leaked an alleged letter to Secretary of Transportation Buttigieg from executives at Boeing and Airbus to David Shepardson of Reuters. No one has published the full text of the letter, but it seems to forecast dire consequences.

“5G interference could adversely affect the ability of aircraft to safely operate,” the letter said, adding it could have “an enormous negative impact on the aviation industry.”

The industry and Federal Aviation Administration (FAA) have raised concerns about potential interference of 5G with sensitive aircraft electronics like radio altimeters.

The FAA this month issued airworthiness directives warning 5G interference could result in flight diversions. The agency plans to provide more information before Jan. 5.

The Boeing Airbus letter cited an analysis from trade group Airlines for America (A4A) that if the FAA 5G directive had been in effect in 2019, about 345,000 passenger flights and 5,400 cargo flights would have faced delays, diversions or cancellations.

This would be an abrupt about-face for Boeing from the position it shared with the FCC during the public comment phase of its enabling regulation. Boeing said a 100 MHz guard band would provide the necessary protection to obsolete altimeters. The FCC responded by more than doubling the guard band to 220 MHz, which should have solved the problem.

Why the About-Face?

There’s nothing wrong with a change of position driven by new and better information. The Boeing letter apparently cites a study by the aviation industry’s lobbyist, Airlines for America:

The Boeing Airbus letter cited an analysis from trade group Airlines for America (A4A) that if the FAA 5G directive had been in effect in 2019, about 345,000 passenger flights and 5,400 cargo flights would have faced delays, diversions or cancellations.

Unfortunately for us the A4A study, like the Boeing/Airbus letter, is secret. While it’s not impossible for lobbyists to produce great technical insights never before seen in public discourse, it’s not exactly routine.

Based on past declarations from the aviation industry, I expect the key variable in A4A’s analysis is supported by nothing but hand-waving. That variable would be the power flux density of the 5G mid-band emissions that actually strike altimeters.

Where’s Your Propagation Model, Captain?

We’ve already seen incomplete studies from aviation in this matter. The industry’s think tank, RTCA, shared one a year ago. As we wrote, RTCA had another industry player test some altimeters in a lab setting to see how much power it took in adjacent bands to make them fail.

There would be an answer to that question for any perfectly safe neighboring system, but that’s the easy question rather than the right one. The right question is whether the threshold level is at all likely to exist in the real world.

That’s actually a tricky question because it depends on knowledge the aviation industry lacks. To answer it one needs to understand how 5G signals propagate, how they’re encoded, and how their modulation interacts with airplane surfaces and sensors.

How to Ensure Safety

Setting the safety threshold for the 5G mid-band needs to be a collaborative effort because neither the aviation nor the wireless industry possesses full and perfect knowledge of the other’s world. Such circumstances occur over and over.

We’ve faced similar problems in determining the effect of potential interference between unlicensed 5G and Wi-Fi, Wi-Fi and Bluetooth, GPS and cellular, Wi-Fi 6E and utility networks, and GEO, LEO, and terrestrial data services in 12 GHz.

Answering questions about radio interference is what the FCC and NTIA’s Institute for Telecommunications Sciences do for a living and they’re rarely wrong. But the FCC and ITS approach it as an engineering question while aviation has other priorities.

A Heavily Subsidized Industry

Aviation’s priorities were on display in last week’s oversight hearing in the Senate. While most industries have weathered the worst of the COVID-19 pandemic to date with the Paycheck Protection Program, aviation got its own special deal, the much more generous Payroll Support Program (PSP).

The hearing was a described by members as a lovefest, and that was putting it mildly. Missing from the hearing was discussion of aviation’s rapacious spectrum appetite; only Senators Blackburn and Young brought it up, and then only briefly.

None of the witnesses mentioned 5G in their written or oral statements, and when asked they emphasized that their worry was the FAA’s rash flight restrictions rather than any sort of real operational issue. Go to 2:01:35 in the hearing video to hear the head of Southwest Airlines on the FAA’s erratic behavior.

Airlines Aren’t Rocking the Boat

If this were a real problem, the CEOs who testified to Senate Commerce on December 15th would have raised it on their own. The fact that they didn’t ask for FCC intervention when pressed is also telling.

So what we have there is the judgment of a lobbying group looking to keep its sugar daddy regulator happy and two vulnerable firms – with somewhat checkered safety histories – playing the same game.

The FAA is perfectly within its authority to ground aircraft for safety reasons, but it needs to be held accountable for emergency orders that bypass the normal public comment process. Perhaps today’s media shenanigan is an attempt to avoid the next logical step in the administrative law process.

FAA Needs to be Accountable to the Public

A regulator can bypass protocol when necessary, but each such action needs to be temporary. Keeping the 5G mid-band permanently out of the hands of the firms who’ve paid good money for the right to use it is outrageous without good reasons and strong evidence.

If the FAA and the industry it regulates can produce such data, I’d like to be the first to praise it for doing such great work. But it’s a long way from clearing that bar.

For starters, they need the measurements of radio propagation in the real world that can inform a realistic predictive model. They don’t have this data because they’ve never put sensors on airplanes and recorded readings. They also don’t appear to have an accurate inventory of all the potentially vulnerable altimeters in the US.

The Money at Stake is Huge

Investment dynamics are probably hard for government agencies to grasp. In this instance, the bidders who won the mid-band auction paid a premium for rapid clearing. They’re now getting robbed by the FAA because once clear spectrum is no longer useable.

It’s not conventional for agencies to compensate industries for their costly errors, but aviation is in a unique position thanks to the PSP. If the FAA and the airlines really believe that 5G poses an unacceptable risk to aviation, then let them use their PSP money to license the spectrum at issue until the problem is solved.

Faced with a choice between using the PSP subsidy for spectrum rights and spending it on route expansion, I’ve got a pretty good idea of the choice they’ll make. To understand how changes in tax law, spending for expedited clearing, and bidding for licenses interact with the FAA’s probably imaginary fears, see this column by Roger Entner.

In brief, the FAA has a lot of explaining to do. Instead of playing this game of media leak-a-thon with secret studies and mystical data, the time has come for the FAA to come clean and show its cards.

UPDATE: A4A and CTIA agreed today (Dec. 22) to share data. That was quick.