A failed backup telecommunications line led to a 90-second radar and radio outage last month that left air traffic controllers unable to see jetliners heading into Newark airport.After the primary connection that carries radar data into the Philadelphia facility where controllers guide planes into the busy hub failed,

The air traffic control mishap early Friday morning added to disruptions in recent days that have intensified concerns about safety at one of the busiest U.S. airports.

Another radar outage at the Philadelphia TRACON has triggered flight disruptions at Newark airport, marking the third failure in two weeks.