The video display system that tracks all aircraft crossing from the American West Coast to destinations in Hawaii and South-east Asia suffered a total failure when engineers were trying to install new software. Roughly 500 aircraft, many of the jumbo jets, were affected, officials said.
During the Pacific blackout, which began on Wednesday evening, traffic controllers at the Oakland centre were reduced to tracking the progress of planes with pen and paper.
Government officials insisted that passengers were not seriously imperiled, in part because of the sheer size of the airspace involved - 18 million square miles, or one tenth of the Earth's surface.
The controllers themselves expressed concern, however. "Was there any real danger that two planes would collide? No. Was there an increase in the potential danger? Yes," said Mike Ballard, president of the Oakland chapter of the National Air Traffic Controllers' Association.
The software installation that caused the fritz is part of a nationwide effort by the US government to upgrade an air traffic control system that has long been criticised for being antiquated and prone to meltdown.
Another control collapse caused major delays and reroutings across the Midwest just before Christmas.
Blaming the Federal Aviation Authority for this week's incident, Mr Ballard commented: "It's another example of the FAA's failure to modernise in a timely manner, which is leaving the public at risk".