All flights into and out of Ronald Reagan National Airport, one of the nation's busiest airports, were halted for a time Tuesday due to a reported bomb threat, federal authorities announced.

The threat was directed towards a United Airlines flight traveling from Houston, Texas to the Washington, D.C. area airport, U.S. Department of Transportation Secretary Sean Duffy said on X.

All other flights were put on hold while the aircraft was moved to an isolated area of the airport. The 89 passengers and six crew members disembarked from the Boeing 737 plane and were bussed to the terminal, United Airlines and the Metropolitan Washington Airports Authority said.

The FBI Washington Field Office’s National Capital Response Squad responded to the reported threat and said no hazardous materials were found. Law enforcement is now investigating the threat itself, authorities said.

All airport operations resumed at approximately 1:30 p.m. ET, according to Duffy, who thanked law enforcement for responding swiftly.

Before flights resumed, the average delay time for departing flights outside of the airport was 51 minutes on Tuesday afternoon, according to the the Federal Aviation Administration. The maximum delay time was over two hours.

Flight delays across the country have been on the rise as the federal government enters the second month of a shutdown, leaving air traffic controllers to work without pay.

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The agency's name has been corrected to the Federation Aviation Administration, not the Federal Aviation Authority.

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Associated Press reporter Mike Balsamo contributed reporting from Washington, D.C.