Japanese companies led by Mitsubishi Heavy Industries Ltd maker of the wartime Zero fighter, build a third of the Dreamliner including its wings. With each succeeding Boeing model, Japanese suppliers have deepened their involvement from supplying parts for the 747 jumbo jet to becoming full-fledged, risk-sharing partners with the U.S. aircraft builder.

The stake of Japanese suppliers rose from less than a fifth for the 767 to a quarter for the 777 and 35 percent for the 787. As many as 22,000 aerospace jobs at 65 firms in Japan are pegged to Boeing’s fortunes, Boeing estimates.

After years of trying, Europe’s Airbus has failed to drive a wedge into Japan’s ties to Boeing, which in the past decade has won more than 80 percent of Japan’s aircraft orders.

POTENTIAL DAMAGE

For now, Japan is sticking by Boeing with some even calling for a more conspicuous government support for the 787.

“I didn’t feel there was enough (government) effort to promote the 787,” said Hiroyasu Hagio, a former JAL pilot who represented flight crews in the 2008 review as head of the Japan Aircraft Pilot Association. He added: “In other countries it’s normal for countries to aggressively get involved in sales.”

The two big Japanese carriers remain committed to putting the 787 at the core of their fleet planning and say there has been no change to their order plans.

But there are signs the Dreamliner’s problems have strained ties between Japan and Boeing. Last week, U.S. diplomats met Japanese officials in Tokyo to discuss the political and economic fallout from the Dreamliner’s grounding.

“If Boeing intentionally and politically puts the losses on to Japanese companies, the damage for Japan will be huge,” said Isao Iijima, a political adviser to Prime Minister Shinzo Abe. (Additional reporting by Maki Shiraki, James Topham, Antoni Slodkowski and Yumi Muranaka; Editing by Kevin Krolicki and Ian Geoghegan)