Boeing (BA 0.25%) has spent the past week meeting with transportation safety regulators first in the United States and now in Japan, pushing a plan to fix the concerns that have had the 787 Dreamliner grounded since mid-January. Boeing's customers are losing money and Boeing's reputation suffers every day the planes aren't flying, so Boeing would like to get the planes back in the air as soon as April.

Boeing has traced the problems, which have included smoke infiltrating the plane cabin and even a small fire, to large, advanced lithium ion batteries in the plane's wing, which can overheat. While investigators don't yet know what causes the batteries to overheat in the first place, Boeing's fix involves mitigating this event by insulating the batteries, surrounding them in a fireproof case, and venting gases that could build up inside the battery compartment.

While the U.S. Federal Aviation Administration is not yet ready to allow test flights , Japanese regulators aren't even ready to admit that the battery itself is the problem, according to The New York Times. At a press conference, Japanese transport minister Akihiro Ota called Boeing's plan a "starting point" and indicated that his ministry would need to take some time just to evaluate the proposal to see if its satisfactory. If Japanese regulators don't accept that the battery is at fault, and require Boeing to go back to the drawing board for a more comprehensive fix, resuming flights by April would look very unrealistic.

There may be a bit of nationalist pride in Japan's regulatory position here: The batteries in question were produced by GS Yuasa, a Japanese company. That nationalism could hurt Boeing now, but it has certainly helped in the past. I doubt it's any accident that Japanese suppliers produced around a third of the Dreamliner, a larger portion than any other country, and Japanese national airlines have been the biggest customers for the Dreamliner.

Japanese airlines, including launch customer All Nippon Airways and Japanese national flag-carrier Japan Airlines, between them operate around half of the global 787 fleet. In the U.S., just six Dreamliners have been delivered nationwide, all of them to United Air Lines (UAL -1.25%).

Japan's preponderance of Dreamliners means that even though Boeing is an iconic American company, Japanese regulators actually have far more clout than US regulators in determining when and how the 787 gets back in the air. Of course, Japan's heavy investment in the Dreamliner also means the nation has a strong incentive to get the plane back in the air as quickly and safely as possible.