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

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.

A backup software system at Newark Airport prevented a third radar outage, ensuring operations continued despite the primary system failing.