Colorado Air Traffic Control Facility Lost Contact With Pilots

Part of an air traffic control facility in Colorado that coordinates flights over a large swath of the West had a 90-second communications outage on Monday, the Federal Aviation Administration said on Thursday.

The outage occurred after a different air traffic control facility in Philadelphia had two radar outages in recent weeks that left controllers unable to communicate with planes headed to or from Newark Liberty International Airport, a major international hub near New York.

The Colorado outage occurred around 1:50 p.m. when a pair of transmitters that cover a portion of the airspace went down.

“Controllers used another frequency to relay instructions to pilots,” the aviation agency said. “Aircraft remained safely separated and there were no impacts to operations. The F.A.A. is investigating.”

Unlike the Philadelphia facility, which mainly guides planes landing at or taking off from Newark, the facility in Colorado oversees planes during their journeys. The aircraft are typically higher in the sky, more spaced out and moving at steady speeds. There are about two dozen such facilities nationwide each covering more than 100,000 square miles of airspace.

The outage was reported earlier by the ABC affiliate Denver7. According to the station, almost two dozen pilots headed to Denver International Airport were unable to contact air traffic control for six minutes on Monday afternoon.

According to FlightAware, a flight tracking service, the Denver airport, the biggest in Colorado, had a relatively uneventful day on Monday. Just two flights were canceled and fewer than 300 had been delayed. United Airlines is the largest airline at the airport, commanding about 38 percent of flights there. Southwest Airlines is the next largest, with a 32 percent share, according to federal data.

In a statement, United said the outage did not disrupt its operations. Southwest did not immediately respond to a request for comment.