“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.

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.

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