The air traffic control tower in Las Vegas was shut down after an air traffic controller potentially tested positive for COVID-19. It apparently was being cleaned overnight.

McCarran International Airport was virtually empty of passengers and workers Wednesday, March 18, 2020, night. (James Schaeffer / Las Vegas Review-Journal)

McCarran International Airport (James Schaeffer/Las Vegas Review-Journal)

A plane passes by the air traffic control tower as it prepares to land at McCarran International Airport on Tuesday, Dec. 18, 2018, in Las Vegas. Benjamin Hager Las Vegas Review-Journal

Slot machines at McCarran International Airport were roped off Wednesday, March 18, 2020, night. (James Schaeffer / Las Vegas Review-Journal)

McCarran International Airport was virtually empty of passengers and workers Wednesday, March 18, 2020, night. (James Schaeffer / Las Vegas Review-Journal)

The air traffic control tower at McCarran International Airport in Las Vegas was temporarily shut down after an air traffic controller potentially tested positive for COVID-19.

The Federal Aviation Administration closed the tower late Wednesday to ensure it’s a safe work environment for air traffic controllers and technicians, after the presumptive positive test, according to a statement from the FAA.

The Las Vegas Terminal Radar Approach Control is still operating, and the airport remains open, with operations continuing at a reduced rate until the situation is resolved, the statement said.

Shelisa Parrish and DeAndre arrived on time for their 1:20 am from Las Vegas to Dallas. After getting through TSA they learned flight was canceled. Now, they’ll leave around 9 am, stop at LAX for a layover and then head to Dallas. pic.twitter.com/YTTdihQepE — Dalton LaFerney 🤖 (@daltonlaferney) March 19, 2020

The air traffic system has multiple backups in place, and the shift in operational control is a regular execution of a well-established contingency plan in place to ensure continued operations, the statement said. Each airport across the country has a similar plan in place that has updated and tested in recent years.

“The safety of our staff and the traveling public is the FAA’s top priority,” spokesman Ian Gregor said in the statement. “Our controllers, inspectors and others with critical safety or security sensitive roles are essential components of our national airspace.”

No information was immediately available on the air traffic controller who tested presumptive positive, or if any others were being tested.

Some flights late Wednesday had been diverted or returned to their origin airports, according to live flight tracking service Flightradar24.

Some travelers at the airport said they were surprised to learn their flights had been canceled.

Shelisa Parrish and DeAndre Horton arrived on time for their 1:20 a.m. flight back home to Dallas. After making it through a security checkpoint, they looked at the departure board and discovered that their flight was canceled.

Now, they’ll be departing McCarran at about 9 a.m. Horton said they would now be flying to Los Angeles for a layover before a flying back to Dallas.

“We’re just gonna sit around and wait for eight hours until it’s time for us to catch our flight,” Parrish said around midnight. “That’s all we really can do.”

It was unclear early Thursday morning whether the cancellation was related to the air traffic controller case.

Another passenger waiting for a ride outside of a terminal said her flight from Dallas was midair when crews announced they might have to stop in Phoenix. The flight didn’t have to make the stop. One group headed to New York found out their flight was canceled about 20 minutes before takeoff.

Passenger volume at McCarran has dropped significantly over the past week because of coronavirus concerns and travel restrictions imposed by President Donald Trump.

Similar case in Chicago

Operations at Chicago’s Midway International Airport were limited Wednesday, a day after federal authorities closed the control tower after technicians tested positive for the novel coronavirus.

The city’s second-largest airport was open, but the FAA said the air traffic control tower was still closed for cleaning.

According to the city’s Department of Aviation, 337 flights had been canceled during the past 24 hours at Midway out of 527 total planned flights. By early afternoon Wednesday, 26 flights were listed as delayed.

“We’re working with the FAA to resume normal operations as quickly and safely as possible which ultimately means having the tower back in service,” the Department of Aviation said in a statement. “Given this reality, and for their own business and network reasons, the airlines are making the decision to cancel many flights.”

Officials said travelers should check with their airline about flight schedules.

Contact Mick Akers at makers@reviewjournal.com or 702-387-2920. Follow @mickakers on Twitter. Review-Journal staff writer Dalton LaFerney and The Associated Press contributed to this report.