GENEVA — Japanese air travel will suffer a major slowdown in the short-term due to the devastating earthquake and tsunami and its recovery will depend on how the nuclear crisis unfolds, the global airline industry’s trade group said Friday.

The burgeoning markets of China, Taiwan, and South Korea are most exposed to a drop in Japanese traffic, with at least a fifth of their air travel revenue coming from business with the country, said the International Air Transport Association.

The next most affected are Thailand, the United States, Hong Kong and Singapore. In Europe, France, Germany and Britain have the busiest air links to Japan.

“The US$62.5 billion Japanese aviation market represents 6.5 per cent of worldwide scheduled traffic and 10 percent of the industry’s revenues. A major slowdown in Japan is expected in the short-term,” said Giovanni Bisignani, who directs the trade group.

“And the fortunes of the industry will likely not improve until the effect of a reconstruction rebound is felt in the second half of the year,” he said.

In its first assessment of the potential impacts of the disasters, the IATA said it’s too early to assess the long-term impact of Japan’s quakes, tsunami and damaged nuclear reactors on the global air transport industry.

The Geneva-based trade group noted that because some Japanese refineries were damaged, prices for jet fuel could rise. The country produces three to fou per cent of global jet fuel supplies, part of that exported in Asia.

Most Japanese airports have enough fuel to last another 10 days, the trade group said, but carriers are trying to work together to make supplies last longer — preparing even for possible “rationing regimes should supply shortages arise.”

The IATA is tracking on its Web site the new regulations that governments are imposing around the world for flights and passengers arriving from Japan.

“The combination of crises and issues facing Japan is truly unprecedented,” Bisignani said. “For aviation, global standards and coordinated efforts will provide the needed solutions.”

The World Health Organization, meanwhile, said Friday that Tokyo’s radiation levels are increasing but still not a health risk and it saw no reason to ban travel to Japan because of its nuclear crisis.

WHO spokesman Gregory Hartl said the UN’s health agency “is not advising travel restrictions to Japan” outside the 30-kilometer (18.6-mile) exclusion zone around the Fukushima Dai-ichi nuclear complex.

He also said that “in general travelers returning from Japan do not represent a health hazard.”