WASHINGTON — Transportation leaders in Congress said the Federal Aviation Administration’s Friday move to stop all U.S. flights from taking off highlights the need to pump more funding into modernizing the agency’s antiquated air traffic control communications systems.

The FAA on Friday afternoon issued a highly unusual nationwide ground stop that caused mass confusion and raised questions about potential terror attacks, or artificial intelligence breakouts resulting from new software the agency is rolling out. The ground stop lasted more than four hours before it was lifted.

Top officials including Homeland Security Secretary Markwayne Mullin tried to quell such fears, chalking it up instead to a “telecommunication outage,” though he said the incident was still under review.

“There is no indication, and we had no reason to believe as of right now, that this was a threat to the United States,” Mullin said. He said the ground stop was implemented “out of an abundance of caution.”

The move to ground all departing flights came after what the FAA called “communication issues” impacting multiple air route traffic control centers, which guide planes across long distances after departure.

Technicians said they were investigating the cause, but by Friday evening the incident had prompted a multiagency response including the broader Transportation Department as well as the State, Defense and Homeland Security departments, Mullin told reporters.

Senate Commerce, Science and Transportation Committee Republicans called the ground stop a “rare but major disruption.” The committee’s majority in a statement added that the outage highlighted the need to prioritize modernization of the air route traffic control centers, pointing out that President Lyndon B. Johnson was in office the last time a new one was built.

The 22 air route traffic control centers across the country guide aircraft using instrument-dependent flight plans. Under such plans, pilots use instruments, electronic navigation and air traffic control assistance to guide them and maintain separation from other aircraft in certain airspaces.

Senate Commerce Republicans touted the $1.9 billion provided to upgrade the facilities in the July 2025 reconciliation law. That package included a total of $12.5 billion for air traffic control modernization.

Transportation Secretary Sean Duffy and Office of Management and Budget Director Russ Vought called the earlier funds a “down-payment” in a Thursday letter to appropriators, asking for an additional $30.1 billion to finish the job. That request includes $10.1 billion for air traffic control upgrades, including $2 billion for “cloud computing and national airspace system telecommunications.”

Commerce Committee ranking member Maria Cantwell, D-Wash., said in a statement Friday night that the panel is looking into FAA and airspace telecommunications issues.

“Technology issues related to how planes communicate through primary frequencies, backup frequencies, and other issues will be something the Commerce Committee will be reviewing,” Cantwell said.

Cantwell is poised to take the committee’s gavel come January as Democrats assume the majority in the Senate.

The committee has also been in monthslong negotiations with leaders of the House Transportation and Infrastructure Committee over dueling aviation safety bills responding to the January 2025 midair collision near Ronald Reagan Washington National Airport that killed 67 people.

At issue in those negotiations is which location transmission technology should be mandated to aid in air traffic control operations and allow aircraft to maintain appropriate distance. Leaders have said they hope to reach a deal in the lame-duck session.

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