Several times over the last year, Newark controllers lost radar or radio service, leaving them unable to talk with planes they were tracking.

“I equate a good, A-level, traffic controller that can handle a place like Newark, JFK, LAX, San Francisco, to a three dimensional chess player who can juggle a chainsaw, an axe, a sword, a razor blade with his eyes closed,” Aero Consulting Experts CEO and a former United pilot Ross Aimer told Fortune.

A reporter asked Duffy on Monday why the first Trump administration chose not to address the air traffic control system during his first term in office, noting that Duffy said it was a “decades-old” problem. However, Duffy’s answer left many users on social media scratching their heads.

Caught in the middle of the issues at Newark is United Airlines, which is the most active airline at the New Jersey airport. While the problems lie with the FAA system, the airline is where people often aim their frustrations over cancellations and delays.

The United States aviation industry continues to grapple with the worst air traffic controller shortage in nearly 30 years as a recent spate of incidents has thrust the high-stress profession into the spotlight.

Duffy laid out an extensive plan to replace the nation’s outdated air traffic control system last week, including installing 4,600 new high-speed data connections and replacing 618 radars, but didn’t put a price tag on the plan other than to say it will cost billions.

One air traffic controller (ATC) and a trainee will operate every flight in and out of Newark between 6.30pm-9.30pm — despite 15 staffers being the standard requirement for a shift.