Flights over parts of the Midwest were being rerouted Friday and the tower at one of New York’s airports temporarily closed in the latest disruptions to the U.S. aviation system as Covid-19 spread to the federal employees responsible for the air-traffic system.

Several routes for cross-country traffic were shut by the Federal Aviation Administration after a supervisor tested positive at the agency’s Indianapolis Center, which oversees high-altitude traffic across several states. Flights were handled by other controllers at the same facility, the FAA said in an emailed statement.

Separately, controllers at New York’s John F. Kennedy International Airport tower are being forced to work in an alternate location after a technician at the facility tested positive for the Covid-19 virus. The airport remains open as the FAA cleans the tower as a precaution, the agency said.

Such disruptions are relatively routine in the air-traffic system and the FAA has long-standing backup procedures to handle them. But the actions on Friday show how quickly the potent coronavirus is spreading and disrupting critical infrastructure.

The impacts of earlier virus-related shutdowns at Chicago’s Midway and Las Vegas McCarran International airports continue to reverberate across the system. More than 1,100 flights were canceled at just those two airports as of 11:10 a.m. Eastern Time, according to the flight-tracking website FlightAware.

About 20% of flights at JFK were also canceled, 259 in total, according to the website. It wasn’t clear how many of the cancellations were due to the tower closure as airlines have been halting international flights in response to the virus, which has cut demand for travel.