The FAA closed its Chicago Midway Air Traffic Control Tower after several technicians there tested positive for Covid-19. Duties at that tower were shifted to the Chicago Terminal Radar Approach Control in Elgin, Illinois, but operators are advised of the potential for delays and a reduced rate of operations.

“The air traffic system is a resilient system with multiple backups in place,” the agency said in a statement. “This shift is a regular execution of a long-standing contingency plan to ensure continued operations. Each facility across the country has a similar plan that has been updated and tested in recent years.” It added that the safety of its staff is a top priority and those employees are an “essential component of our airspace.”

The FAA confirmed the tower would remain closed today but was unclear of the timing on when it would reopen.

Closure came at the request of the National Air Traffic Controllers Association (NATCA), which had urged the FAA to disinfect the tower to ensure it meets appropriate public health standards and coordinate with the local health authority and the Centers for Disease Control and Prevention on testing of all personnel at the tower.

“NATCA is adamant that the testing must occur immediately,” the association said but added it was encouraged that the FAA is moving forward with rapid testing of MDW personnel.