A computer failure at an air traffic control center forced the Federal Aviation Administration to hold planes on the ground at Los Angeles International Airport and other airports in the region on Wednesday afternoon.

The problem at the Los Angeles Air Route Traffic Control Center, which handles higher-altitude aircraft, meant planes bound for the region were also grounded.

Around 4:30 p.m., the Los Angeles International Airport reported that flights had resumed. But delays were expected to last several hours.

Government officials were not immediately sure why the system had failed. Areas affected by the shutdown included Southern California, western Arizona, southern Nevada and part of Utah.