A failure of primary and secondary power supplies caused the outage at Ninoy Aquino airport, and it should take about 72 hours for airlines to normalize their operations, said Cesar Chiong, general manager of the Manila International Airport Authority.

There were 361 flights delayed, canceled or diverted to other regional airports on Sunday, affecting about 65,000 passengers, while may other flights were rerouted around Philippine airspace.

Chiong said the airport was handling a maximum of 15 flights per hour on Monday morning, down from the usual 20.

Several of the airport’s four terminals were crowded on Monday, with long queues of people trying to re-book flights while other weary passengers slept on chairs or on the floor.

“In the 24 hours that we’ve been waiting, we are now very exhausted from lack of sleep, my body is aching from all the waiting,” said Kirana Mangkabong, 32, an overseas worker.

The airport has been ranked among the world’s worst international gateways, with flight backlogs a regular occurrence and a history of upgrades being delayed or abandoned due to disputes between airport authorities and contractors.

Airports are being built in provinces surrounding Manila to relieve pressure, including in Cavite and in Bulacan, which is due to start operations in 2027.

The transport ministry has ruled out sabotage but vowed to investigate the airport chaos, which has renewed calls for existing gateway to be upgraded and better operated.

“The government should look at this wake up call to improve, either through public or private efforts, or a joint venture,” George Barcelon, president of the Philippine Chamber of Commerce and Industry, told Reuters.

His flight from Dubai was affected, as was that of tycoon Manuel Pangilinan, who on Sunday said his flight from Japan had to turn back halfway through and tweeted: “Only in the PH. Sigh.”

Grace Poe, a former presidential candidate and head of the public services committee, called for a congressional inquiry into the incident, saying it was “a national security concern.”

Airport general manager Chiong said that the facility had introduced its own power system in 2018 but that on Sunday, both the main and backup systems failed.

Once connected directly to the regular commercial electricity, the systems experienced a power surge that forced equipment to shut down, including radar and communications, he said.

Joey Concepcion, a government business adviser, said authorities should revive a proposal for a consortium to modernize the airport.

“Any inefficiencies in the airport translate to big losses in business down the line and are felt throughout the country,” he said in a statement.