The operator of Kansai International Airport on Sept. 6 apologized for inconveniencing thousands of travelers after being overwhelmed by a powerful typhoon and announced plans to partially resume domestic flights from the next day.

“We would like to apologize for causing serious trouble,” said Yoshiyuki Yamaya, president of Kansai Airports, the operator, and then bowed at a news conference held for the first time after the airport was paralyzed by the strongest typhoon to hit Japan in 25 years.

Yamaya said the airport will reopen a runway that was relatively unaffected and Terminal 2 to resume domestic flights from Sept. 7.

The airport, built on a man-made island in Osaka Bay, was hit hard on Sept. 4 when Typhoon 21 pounded the Kansai region. High waves submerged one of its two runaways. In addition, a tanker collided with the bridge linking the airport to the mainland, leaving only one side of the divided highway passable.

About 8,000 travelers and airport workers left stranded overnight at the airport had been transported out by midnight on Sept. 5, according to Kansai Airports.

Yamaya said it is not known when the company can reopen the submerged runway, saying electrical equipment stored in the basement area was damaged by seawater.

The night before, Hiroshi Nishio, the company’s corporate executive vice president, admitted when surrounded by reporters that the airport was not equipped to deal with a massive typhoon.

“We geared up for a typhoon, but the typhoon was far stronger than we had expected,” he said. “We were too optimistic.”

Nishio added his company did not anticipate the collision of a tanker with the bridge, either.

Disasters that Kansai Airports has envisaged in its business continuity plan were a powerful earthquake and tsunami, such as one in the Nankai Trough, which sits off southwestern Japan stretching from the Tokai region to the island of Shikoku.

The plan also said “it is highly unlikely that the airport facilities will be submerged in a tsunami.”

In addition, the plan did not anticipate an emergency in which the airport bridge would be closed for a prolonged period. It stated a “lifeline will be restored in a short period of time.”

But the disaster response center, located in the basement floor of the passenger terminal building, was rendered unusable after it was inundated by high waves.

“We will consider measures to reinforce the facility based on the lessons we learned this time,” Nishio said.

The airport closed both runways at noon of Sept. 4 with the approach of Typhoon 21.

But the operator apparently believed that it could ride out the storm without much difficulty.

“Ahead of the closure of the runways, the airport said it expects to resume operations by the evening of that day,” an official in the airline industry said.

But the first runway was swamped by record-high 329-centimeter waves at 2:18 p.m., exceeding the highest level produced by a powerful typhoon in 1961, which the airport had been prepared to cope with.

The number of airport staff members working that day was fewer than usual because the operator arranged in advance for only the necessary minimum to report to work.

That compounded the difficulty of passengers stranded at the airport who were desperate for any updates about their predicament.

“I had no clue as to what was going on from the start to the finish,” said a 33-year-old company employee from Kyoto.

A power failure occurred at the airport terminal building at 1:30 p.m. on Sept. 4 and power had not been restored as of the night of Sept. 5. The telecommunication system has yet to be put fully back online.

Airline companies were also busy coping with the fallout.

All Nippon Airways Co. said it needed to inspect its nearly 10 airplanes in the tarmac as the tires of some were submerged in seawater up to half their height. Hundreds of the airline's work vehicles and maintenance facilities were also inundated.

Japan Airlines Co. is trying to assess the damage from the flooding. Its aircraft were all inside a hangar.

Kansai International Airport is a gateway to western Japan, with 1,366 flights a week and more than 15 million travelers arriving each year.

Hotels and travel agencies in the Kansai region have already reported a flurry of reservation cancellations.

Akira Yoshimura, a manager in the economic research division at MUFJ Bank, said the sooner the airport can resume operations, the better.

“If it takes longer for the airport to resume operations, it could not only cause a decline in the number of foreign tourist arrivals, but also a delay in the recovery of their arrivals,” he said.