A technical problem at an air traffic control center in Virginia that caused hundreds of flights to be delayed or canceled along a large swath of the East Coast was possibly caused by a software upgrade, according to a statement from the Federal Aviation Administration on Sunday.

The FAA said the upgrade was designed to provide more tools for controllers, but that the new features have been disabled while the systems contractor completes an assessment of the malfunction.

There were roughly 492 delays and 476 cancellations related to the technical problem, the agency said, which resulted in about 70 percent of normal Saturday air traffic at the Baltimore-Washington International Airport, 72 percent at Ronald Reagan Washington National Airport and 88 percent at Dulles International Airport. Part of the backlog was the result of a decision to reduce arrival and departure rates in the Washington area between 11 a.m. and 4 p.m. on Saturday for safety reasons.

Flights departing from Newark Liberty International Airport in New Jersey and John F. Kennedy and LaGuardia airports in New York that normally flight over the Washington region as they head southward were also affected, although the FAA had said it was trying to route the flights around the affected area.

The FAA initially blamed the problem on “technical issues” at an air traffic control center in Leesburg, Virginia. About 4 p.m., the agency said the problem had been resolved, and that officials were working to lift any remaining orders to hold planes on the ground.

By midafternoon, 50 percent of inbound flights and 42 percent of outbound flights had been canceled at Reagan National, and delays were averaging about three hours, according to FlightRadar24. In Baltimore, 58 percent of inbound flights and 36 of outbound flights had been canceled, and delays were averaging more than an hour.

Information posted by the agency Saturday suggested the problem was with the En Route Automation Modernization computer system, known as ERAM, at the Leesburg Center. The agency on Sunday confirmed that the problematic upgrade was to this computer system, however there is “no indication that the problem is related to any inherent problems with the En Route Automation Modernization system, which has had a greater than 99.99 availability rate since it was completed nationwide earlier this year.”

(AP)