Flights were halted at the Washington area’s Reagan National Airport on Tuesday after a report of a bomb threat targeting an inbound United Airlines flight, according to Transportation Secretary Sean P. Duffy.

Arrivals and departures stopped for about 90 minutes, according to flight-tracking data. The United plane landed and parked at the side of the airport and passengers were evacuated while law enforcement searched the jet, Duffy said. The FBI also responded to reports of the bomb threat and said “no hazards were found,” according to a post on X.

A person called the airport’s control tower seeking a $500,000 payment in cryptocurrency, according to multiple people familiar with the incident who spoke on the condition of anonymity because of the sensitivity of the situation. The caller said the plane would explode when it landed, according to the people.

“I want to thank our brave men and women in law enforcement for their quick response,” Duffy said in a post on X.

According to United Airlines, there were 89 passengers and six crew members aboard the Boeing 737 Max 8 jet, which originated in Houston and landed at National around 11:20 a.m.

In a statement, the carrier said Flight 512 landed safety “after a potential security concern.”

Passengers were taken off the plane and bused to the terminal and the aircraft was searched and cleared, United said.

Several flights were diverted to other airports in Maryland and Virginia while the situation unfolded on the ground, according to tracking data from Flightradar24.

This is the second time this week that a potential bomb threat caused flight delays. On Monday, a threatening note was discovered in a lavatory of Frontier Airlines Flight 1324 at Dallas-Fort Worth International Airport, according to a statement from the carrier. The flight, which originated in Denver, landed safely at the airport where it was met by local law enforcement and the FBI, who determined there was no threat. The jet was cleared and passengers were deplaned at the terminal, according to airport officials.

The disruptions come amid heightened scrutiny of the national airspace system as the government shutdown stretches into a second month. Air traffic controllers and Transportation Security Administration officers are among the federal employees working without pay. Though there have been sporadic spikes in flight disruptions tied to staffing shortages, the system has been relatively stable. However on Tuesday, Transportation Secretary Sean P. Duffy warned that officials could be forced to shut down portions of the national airspace if not enough air traffic controllers show up for work.