CHICAGO (CBS) — Three days after the FAA closed the air traffic control tower at Midway International Airport, and moved operations to another facility, Southwest Airlines has significantly reduced its operations at Midway.

“We have reduced operations at the Chicago Midway airport due to the closure of the FAA ATC tower in the Chicago area,” Southwest Airlines spokesperson Ro Hawthorne wrote in an email.

The move resulted in more than 173 canceled flights on Friday, and Hawthorne said the airline is averaging four to six flights an hour.

The airline originally said it had ceased operations at Midway, but later issued a correction.

The air traffic control tower at Midway was closed Tuesday evening, and operations for Midway were moved to the Chicago TRACON radar facility in Elgin, after three tower workers tested positive for coronavirus. At the time, the FAA said airport operations would continue at a reduced rate until the situation was resolved.

CBS News reports the airport was moved to a “one flight in, one flight out” approach for flights. Arriving and departing pilots will announce themselves over a common radio channel, essentially the same procedure for how one would fly into a municipal airport without a tower. Once airborne, pilots will communicate with Chicago TRACON, an FAA radar facility in Elgin. Departures will organize by departure time, and hold short of the runway until the arriving plane clears. Then the first one up will announce and take off.

The FAA’s longstanding contingency plans call for services to fall back to Chicago TRACON in the event the tower goes dark. TRACON is the regional air traffic control hub that controls airspace after a plane leaves the main tower’s immediate vicinity.

“The air traffic system is a resilient system with multiple backups in place. This shift is a regular execution of a longstanding contingency plan to ensure continued operations. Each facility across the country has a similar plan that has been updated and tested in recent years,” the FAA said. “The safety of our staff and the traveling public is the FAA’s top priority. Our controllers, inspectors and others with critical safety or security sensitive roles are essential components of our national airspace.”

The FAA did not immediately respond Friday when CBS 2 asked when the Midway tower would reopen.

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