NEWARK, N.J. (AP) -- The National Transportation Safety Board says a close call at Newark Liberty International Airport involving two airliners that nearly collided was the fault of an air traffic controller who didn't keep the planes far enough apart.

Newark Liberty International Airport Terminal B (Jeff Zelevansky/Getty Images)

NJ.com reports the NTSB says in a report issued Wednesday that the planes missed each other by just 400 feet. One ducked under the other as it abruptly aborted its landing in April 2014.

An ExpressJet flight was departing for Memphis on a northbound runway as a United flight from San Francisco was approaching to land on an east-west runway.

A National Air Traffic Controllers Association spokesman had no comment.

FAA spokesman Jim Peters says the agency instituted refresher training for workers at the control tower following the incident.