Over the past two weeks, several equipment outages at the Philadelphia-based air traffic control center that guides planes to and from Newark Liberty International Airport, have raised questions on just how safe it is to fly at one of the nation’s busiest airports.

For the third time in two weeks, Newark Liberty International Airport air traffic controllers overseeing the busy New Jersey airport were temporarily unable to contact pilots.

Technology and staffing problems have plagued the airport, one of the nation’s busiest hubs. Officials say they are trying to resolve the issues, but concerns remain.