Air traffic controllers at Newark Liberty International Airport briefly lost communications with planes under their control, "unable to see, hear, or talk to them" last week, officials say. The Federal Aviation Administration also acknowledged in a statement that "our antiquated air traffic control system is affecting our work force". The National Air Traffic Controllers Association said the employees took leave under provisions for workers who experience a traumatic event at work. The union would not say how many controllers had taken leave, or how long they lost contact with planes. The incident comes as the US Department of Transportation last week unveiled a package designed to boost the numbers of FAA air traffic controllers.