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 about how safe it is to fly at one of the nation’s busiest airports.

A 45-minute-long ground stop at Newark Liberty International Airport has been lifted. The ground stop was put in place by the FAA in response to an air traffic control equipment outage. This outage comes after two similar equipment outage incidents – one on April 28 and the other on May 9.

The airport has been been beset by flight delays and cancellations brought on by a shortage of air traffic controllers.