The Federal Aviation Administration briefly halted departures from New York and Philadelphia airports after a trainee at the New York Air Route Traffic Control Center in Long Island tested positive for COVID-19 today. The person had not been at the facility since March 17th, and the FAA is sanitizing affected areas.

As of 2:45 PM ET, the agency had lifted the ground stop order, according to the Associated Press.

The Long Island center, which primarily handles high-altitude, cross-country flights, remained open. But the FAA rerouted flights “as part of a longstanding contingency plan to ensure continued operations.”

The FAA said in a statement that it is “working with local health officials and employee representatives to determine how many personnel might have interacted with the trainee in recent days.”

CNBC reported that there have been staffing issues because of coronavirus at FAA facilities around the country; on Wednesday, flights from McCarran International Airport in Las Vegas were diverted because an air traffic controller there “potentially tested positive” for COVID-19.

Update March 21st 2:51PM ET: Adds that the FAA lifted the ground stop order