NEW YORK — The Federal Aviation Administration reported delays in air travel Friday because of a “slight increase in sick leave” at two East Coast air traffic control facilities.

The delays come as a partial government shutdown threatens to undermine the nation’s air travel system. Air traffic controllers and airport security agents have been working without pay since the federal shutdown began in December, but high absentee rates raise the possibility of long airport lines, or even worse.

The White House spokeswoman Sarah Sanders said President Donald Trump has been briefed on the delays and “we are monitoring the ongoing delays at some airports.”

“We are in regular contact with officials at the Department of Transportation and the FAA,” Sanders said in a statement.

New York Gov. Andrew Cuomo wrote a letter to Trump earlier Friday saying the shutdown is impacting safety and security at airports and putting travelers at risk.

FAA spokesman Gregory Martin said Friday that it had augmented staffing, rerouted traffic and increased spacing between planes as needed.

The staffing problems were at air traffic centers in Jacksonville, Florida and a Washington D.C. center that controls high-altitude air traffic over seven states.

“The results have been minimal impacts to efficiency while maintaining consistent levels of safety in the national airspace system,” Martin said in an emailed statement.

LaGuardia Airport in New York and Newark Liberty International Airport in New Jersey were both experiencing at least 90-minute delays in takeoffs Friday.

Sanjay Shetty was waiting at LaGuardia to board a flight to Detroit when he heard an announcement about a ground stop due to a “staff shortage” around 10:15 a.m. He said he and other passengers eventually started boarding at 10:50 a.m. — the plane’s scheduled departure time. It wasn’t clear when they would get off the ground.

“The shutdown hadn’t affected me until now,” the management consultant from Ann Arbor, Michigan, tweeted.

Meanwhile, the Transportation Security Administration said in a statement that Hartsfield-Jackson Atlanta International Airport had maximum wait times Thursday of 42 minutes, the highest of the nation’s top 42 airports.

Baltimore/Washington International Thurgood Marshall Airport had the second-longest wait time, of 19 minutes.