Flights to and from airports in the Los Angeles area were grounded for more than an hour Wednesday because of a computer failure at an air traffic control facility, the Federal Aviation Administration said.

The problems rippled nationwide. Dozens of planes heading into the region were diverted, and flights scheduled to take off to the Los Angeles area were held on the ground across the country.

The “ground stop” affected airports including Los Angeles International, the nation’s third busiest, where more than 30 flights were prevented from taking off, an airport spokeswoman said.

Flights closing in on the area’s airports were allowed to land. But planes that were farther away were diverted to Phoenix, Las Vegas, Salt Lake City and elsewhere.

Fifteen flights bound for Los Angeles landed in Phoenix, and five in Salt Lake City, officials at those cities’ airports said.

Officials at Bob Hope Airport in Burbank, near Los Angeles, said flights were held from 1:50 to 3:20 p.m. Pacific time.

A notice posted on the FAA Web site said planes were not allowed to depart Los Angeles because of a failure within the agency’s En Route Automation Modernization system, also known as ERAM.

The computer system allows air traffic controllers at several dozen “en route centers” around the country to identify and direct planes at high altitudes.

The Los Angeles “en route center” is at the Palmdale Regional Airport, about 40 miles to the north. It controls high-altitude air traffic over southern and central California, southern Nevada, southwestern Utah and western Arizona — except for airspace designated for military use.

Planes flying at lower altitudes are directed by approach control centers and local airport towers.

ERAM is critical to the FAA’s plans to transition from a radar-based air traffic control system to satellite-based navigation, but its rollout is years behind schedule and hundreds of millions of dollars over budget.

ERAM is replacing another computer system that was so old that most of the technicians who understood its unique computer language have retired.