Japan Airlines slashed flights to Hawaii, China, and South Korea after an earthquake and nuclear crisis caused a 25 percent drop in its international passenger numbers.

The cuts, mainly affecting Tokyo Narita Airport services, will run from April 6 to about April 27, the carrier said in an e-mailed statement today. Skymark Airlines Inc., Japan’s largest low-cost carrier, will halt flights at Ibaraki airport, northeast of Tokyo, for five days from March 30 to wash plane engines as a precaution, spokesman Yusuke Tanaka said by phone.

JAL’s domestic loads have also fallen 28 percent since the March 11 quake compared with a year earlier, President Masaru Onishi told reporters in Tokyo, as concerns about radiation leaking from a nuclear-power plant and power shortages damp travel to the capital. Singapore Airlines Ltd. and Asiana Airlines Inc. have already announced Tokyo flight cuts, while Qantas Airways Ltd.’s budget unit Jetstar has moved some services to Osaka.

JAL’s cuts at Narita airport include halting Hong Kong services, halving Beijing flights to seven a week and paring Honolulu to 14 trips a week from 21. The reductions also cover Shanghai, Seoul, Pusan and Taipei. The airline will continue flying to Hong Kong from Tokyo’s Haneda airport, it said.

Skymark hasn’t detected radiation on its planes, Tanaka said. The carrier operates flights from Ibaraki to Kobe, Sapporo and Chubu airport. The airport is closer to the area hit by the tsunami and the crippled Fukushima Dai-Ichi plant than Narita or Haneda.

Seoul-based Asiana has halted flights to Ibaraki through June 30 and it has cut flights to other airports including Haneda, according to a notice on its website. Shanghai-based Spring Airlines Co. has halted flights to Ibaraki through March 30, according to its website.

Current levels of radiation at the airport give no cause for concern, Kazunori Katsutani, a director, said today.