A technical outage in Philadelphia last week terrified air traffic controllers and stranded passengers. As the summer travel season looms, the F.A.A. is racing to address the problems.

Travelers flying in and out of New Jersey's Newark Liberty International Airport were increasingly edgy about a host of recent problems at the busy airport, but they were most alarmed about two separate equipment outages in the last two weeks that disrupted communications between air traffic controllers and pilots.

Another outage of air traffic control radar and communications equipment happened at Newark airport in the early hours of May 9. The airport has been struggling with mass delays and cancellations after a similar outage happened on April 28.