The Federal Aviation Administration said late Saturday that 11 of its air traffic control facilities nationwide have employees who have tested positive for covid-19.

They include the New York Air Route Traffic Control Center in Long Island, which handles a broad swath of airspace; the air traffic control towers at John F. Kennedy International (JFK) and LaGuardia airports in New York; executive airports in Leesburg, Va., and Long Island; and facilities in Peoria, Ill. and Wilmington, De., in addition to previously reported cases in Las Vegas, Indianapolis and Chicago.

Widespread disruptions were seen Saturday after an air traffic control trainee and others in New York tested positive, according to the FAA.

The FAA said it was not specifying the total number of employees infected because the numbers keep changing.

“Like much of the country, the Federal Aviation Administration is experiencing an increase in COVID-19 cases at air traffic facilities and other offices across the nation,” the agency said in a statement. “Despite the challenges, our commitment to safety will not waver.”

Demand for aviation has plummeted with the spread of the virus, hammering airlines, though significant numbers of travelers are still taking to the air.

The FAA described actions it is taking to keep planes flying and its employees safe, including “transferring duties” to other facilities; closing the LaGuardia control tower and the New York air route center for overnight cleaning Saturday night through early Sunday morning; working to disinfect other facilities; and tracing contacts between the infected workers and their colleagues and others.

“Each disruption has a distinct impact on the air traffic system,” the agency said. “This is frustrating and inconvenient, but is necessary in the interest of safety.”

The agency said the “effects on traffic” because of the overnight New York closures “are expected to be minimal due to the low volume during those hours.” It said other facilities “will provide key services” during that time.

Earlier Saturday, the FAA also pointed to limited supplies of basic cleaning products, such as wipes and sanitizer, as a challenge at some of its facilities. Shortages of masks and test kits have hampered the U.S. response to the novel coronavirus.

“We are restocking cleaning supplies at air traffic facilities where they are running low,” the FAA said in a statement. “As an interim measure, the agency has authorized managers to purchase cleaning products at local stores if needed to sanitize workspaces. We are not requiring employees to bring supplies from home, although some employees are doing so voluntarily.”

The acknowledgment came after Rep. Jennifer Wexton (D-Va.) pressed the agency last week on the availability of cleaning supplies for FAA employees.

On Saturday, a trainee at the New York Air Route Traffic Control Center and an employe or employees at LaGuardia air traffic control tower tested positive, the agency said.The FAA also said Saturday that personnel at JFK’s tower tested positive on Thursday, and that operations there were “temporarily moved to an alternative site during cleaning.”

On Saturday, major flight restrictions affected airports around the country.

Even as the FAA said in a statement that it may have to close “sectors of airspace during the sanitization process,” the FAA issued “ground stops” Saturday for New York’s JFK and Philadelphia International Airport, among others.

That meant flights headed for those airports were not permitted to take off from their original airports. And if they had already taken off, they could be held in the air or diverted to other places depending on how long the restrictions were in place.

The restrictions were quickly lifted on Philadelphia and some other locations but stayed in effect longer at JFK. Planes headed there from Florida, Texas, Georgia and the D.C. region were all blocked by the JFK ground stop Saturday afternoon, but the limits were later removed, according to an FAA notice.

Earlier positive tests by employees in air traffic control towers at Chicago’s Midway airport and elsewhere have also prompted closures for cleaning in recent days.

FAA administrator Steve Dickson is under self-quarantine after having a “brief interaction” with Rep. Mario Diaz-Balart (R-Fla.), who has tested positive, before a House hearing earlier this month.

Wexton wrote the FAA on Thursday, raising concerns from employees about sanitation and the need for additional teleworking.

“We received word that ‘no action is required until a case is confirmed positive by a medical authority’ and that the extent of action taken so far has been to advise facilities to make local purchases of cleaning supplies while the FAA takes steps to find other sources of cleaning products and establish enhanced cleaning protocols,” Wexton wrote.

Wexton said in a statement that it is “absolutely unacceptable that the FAA has not implemented critical measures to safeguard the health of its workforce,” and that the “well-being of our air traffic controllers is vital to preserving not only the safety of our airspace but also our national security.”

The FAA said Saturday that it is “encouraging all eligible employees to telework to the maximum extent possible” and has limited outsiders from FAA facilities to prevent the spread of coronavirus.

Still, it added, “many employees perform critical functions that cannot be handled remotely.” In such cases, “we are employing social distancing measures and increasing the cleaning of workspaces to reduce risk of exposure,” the agency said. Contingency plans are in place to make sure oversight of airlines and aviation safety do not suffer, it said.

“In extreme cases, service levels could vary, but safety will not be compromised,” the agency said.

In responses it provided to Wexton, the FAA said its Air Traffic Organization “is asking our facilities to make local purchases for cleaners, wipes, and hand sanitizer where possible” and the agency is “supplementing supplies from our Logistics Center as best we can.”

“Cleaning materials that meet the criteria are in short supply across the marketplace, and we may face further challenges maintaining adequate quantities,” the agency said. The FAA said it is searching for vendors to make and deliver cleaning products to the agency to support the work of air traffic controllers.

“We also continue to reach out to FEMA and DOD to see if they can help augment our supplies,” the FAA said, referring to the Federal Emergency Management Agency and the Department of Defense.

In an added statement Saturday, the FAA said, “with the exception of a couple of isolated cases, we have adequate supplies nationally.” It said “restocking to ensure the health and safety of our workforce is a priority.”

The infected employee or employees in the air traffic control tower at Leesburg Executive Airport tested positive Saturday, as did personnel at LaGuardia and in Peoria, the FAA said. The positive test or tests in Wilmington came Friday, it said.

Employees at two separate facilities at McCarran International Airport in Las Vegas tested positive. The air traffic control tower there remained closed as of Saturday night, as workers were “cleaning to standards,” the FAA said, but the McCarran Terminal Radar Approach Control Facility was operating.

Operations are normal at the Republic Airport in Long Island, and in Leesburg, the FAA said.

Additional updates on particular airports and potential new cases can be found here.

Staff writer Ian Duncan contributed to this report