After the incident last month at Reagan National, the union demanded that additional controllers be added at towers where a single person worked on midnight shifts as a safety measure to limit the risks that a controller could fall asleep.

“Once again, we’ve got a midnight shift issue,” Church said. “Those are very concerning to us. We believe that staffing always needs to be what’s looked at, here and at other facilities.”

Typically, air-traffic facilities are designed with enough flexibility that controllers in a tower can handle traffic far outside an airport. In most cases at small and midsize airports, controllers are trained to handle both landings and takeoffs as well as higher altitude traffic.