An unusual public dispute among federal agencies is playing out in Washington, delaying the rollout of 5G cellphone services and revealing government infighting that has plagued two U.S. administrations.
AT&T Inc. and Verizon Communications Inc. earlier this month said they would delay the launch of some fifth-generation wireless services after the Federal Aviation Administration warned it could restrict U.S. airspace in bad weather if the networks were turned on as planned in December. The FAA warning came in the thick of cellphone carriers' network upgrade projects.
Almost a year earlier, transportation officials had asked to postpone the government's auction of the airwaves to wireless operators and warned they could impose flight restrictions if not satisfied. The Dec. 1, 2020, letter—sent days before the auction—said the FAA was worried 5G services could interfere with key cockpit safety systems.
Trump administration officials said they didn't agree with the FAA's last-minute concerns, and the Federal Communications Commission went ahead with its auction. Companies like AT&T and Verizon spent $81 billion for the prized licenses , setting a record.
That windfall didn't settle the argument. The air-safety debate that flared up in the final months of the Trump administration, which was eager to advance the country's 5G networks, continued into the Biden administration, which was slow to appoint key FCC and Commerce Department officials who could help resolve the dispute.
Regulators are now working on a tight deadline. FAA officials are tentatively planning to issue restrictions by Dec. 3, people familiar with the matter said. An FAA spokesman said the agency isn't "in a position at the moment to discuss timing on any actions we may or may not take."
The FCC and FAA have said they are working closely together, and both said they are committed to ensuring public safety while advancing the latest broadband technology. To resolve the impasse, the two agencies must work out a compromise. The FCC has allowed cellular service over the airwaves in question, known as C-band, and only its current leaders have the power to tweak those permissions. But if FAA officials aren't satisfied, they have their own power to issue safety warnings that could result in significant flight disruptions.
Cellphone carriers' 5G investments are meanwhile in limbo. A coalition of aerospace manufacturers and industry groups have asked the White House for an open-ended delay to get more detailed knowledge of wireless companies' network deployments.
Telecom companies say a longer wait is a nonstarter. They spent billions of dollars on acceleration payments to ready their spectrum for use within months instead of years.
"There is no scientific or engineering basis for further delay, and we cannot afford to fall behind," the wireless companies' Washington-based trade group, CTIA, said Wednesday. "The wireless industry intends to launch this service in the U.S. next January."
The FAA's 2020 warning wasn't entered into the FCC's docket for public comments. If it had been, it could have prodded experts from both agencies and the industries they regulate to collaborate with more urgency, current and former government officials said. But a last-minute whiff of controversy could have hurt the price of the licenses the government was about to sell.
"It really is theft from these companies, not telling them the whole story," said Diana Furchtgott-Roth, a former Transportation Department official involved with writing the letter. "If the FAA's administrator comes out and says there's danger to planes, that would depress the price."
The letter, signed by then-Transportation Department general counsel Steven Bradbury and FAA chief Steve Dickson, asked for the National Telecommunications and Information Administration's help in deferring the spectrum auction. The NTIA, a Commerce Department unit, often brokers interagency disputes involving wireless spectrum.
The letter flagged possible interference with radar altimeters. The devices feed data to cockpit safety systems that help planes land in poor weather, avoid crashes and prevent midair collisions.
"The aviation industry needs a considerable transition period" to develop, test and retrofit potentially at-risk equipment, they wrote. "Depending on the results of further analysis, it may be appropriate to place restrictions on certain types of operations, which would reduce access to core airports in the U.S."
Then-acting NTIA chief Adam Candeub said in a statement that the FAA's objections received a thorough look despite arriving at the last minute—the federal government had been publicly preparing its auction for years.
"Career NTIA engineers concluded that FAA's data failed to demonstrate a serious threat, and the determination was made to move forward with the auctions after consultation with Commerce officials at the highest level and White House staff," Mr. Candeub said.
Some national regulators have imposed restrictions. France has some limits on 5G operations in place at 17 airports where pilots have less visibility during landing, officials said, while regulations in Japan restrict certain cell sites within 200 meters of an aircraft approach route.
The FAA has in recent years been under pressure from U.S. lawmakers to strengthen its safety oversight after two Boeing Co. 737 MAX jets crashed in Indonesia and Ethiopia in 2018 and 2019, killing 346 people.
On July 14, a coalition of aviation industry groups wrote to Transportation Secretary Pete Buttigieg and Commerce Secretary Gina Raimondo asking for their help to encourage "information sharing from the telecommunications industry" to address an "imminent safety risk," according to a letter reviewed by The Wall Street Journal.
Aviation-safety experts said they lacked details about the locations and power levels of 5G transmissions that could affect aircraft. Telecom-industry leaders have said the aviation industry wasn't sharing basic details about its studies or the type and prevalence of affected altimeters.
The issue gained greater attention within the FAA and Transportation Department during the summer, people familiar with the matter said. By late August, representatives of those agencies were meeting regularly with FCC, Commerce Department and White House officials, people familiar with the matter said.
By autumn, the two sides began sharing information that each had been requesting for months. The FAA on Nov. 2 publicly asked altimeter manufacturers for details about how they could face interference. As of last week, the agency had begun receiving some basic 5G cell-site data, people familiar with the matter said.
Hanging over the talks is the fact that since President Biden took office, neither the FCC or the NTIA, the agency charged with brokering federal spectrum disputes, has had a permanent leader confirmed by the Senate.
The Senate on Wednesday will hold a confirmation hearing for Jessica Rosenworcel, the FCC chairwoman, whose term is up for renewal. Alan Davidson, Mr. Biden's nominee for NTIA administrator, is also up for confirmation.
The federal agencies and the companies they oversee are meanwhile stuck in what New Street Research analyst Blair Levin called "a deep state game of chicken" guided by each regulator's particular interest, with no clear path toward resolution.