What's wrong with the Dreamliner? January 23, 2013 -- Updated 2340 GMT (0740 HKT) U.S. aviation officials evaluating data as part of investigation of 787 problems Dreamliners were grounded last week after fire in Boston, another incident in Japan U.S. officials promise transparency once investigation of Boeing plane complete Fifty Dreamliners flying globally, but Boeing has orders for several hundred Washington (CNN) -- Top U.S. transportation officials said on Wednesday they still have not determined the cause of electrical problems that have grounded the Boeing 787 Dreamliner fleet globally, but added they are continuing a thorough probe and promised transparency once a cause is found. We are evaluating data. We don't know what is causing these incidents yet," Federal Aviation Administration chief Michael Huerta told reporters. Huerta and his boss, Transportation Secretary Ray LaHood, peppered with questions about the grounded plane at an industry event in Washington, promised that the public would be informed about any problems that investigators turn up. "There will be total transparency," LaHood said. People will know what we looked at, what we found, if something needed to be corrected. There will be total transparency. Experts: Quick fix for Dreamliner looks less likely Huerta also explained why the FAA allowed the aircraft to fly on January 11 after a battery caught fire on a plane in Boston -- but grounded it following a 787 emergency landing in Japan four days later prompted by a battery alarm and a report of a burning smell. "The second incident occurred in flight," Huerta said. And that for us was an important consideration where we needed to identify what was causing these power- and battery-related incidents. The National Transportation Safety Board, the FAA, Japanese aviation authorities, and Boeing are investigating the matter. During an address at the event, LaHood expressed confidence in Boeing's ability to build safe aircraft. "Our goal is to get this (Dreamliner review) done as quickly as possible," he said, adding that the FAA needs "to get to the bottom of the recent issues." Currently, United Airlines is the only U.S. airline with 787s with six. Worldwide, there are 50 in service but several hundred on order at Boeing. LaHood declined to speculate on how long the FAA's review would take. I'm not going to comment in the middle of their review. Frankly I haven't talked to them," LaHood said. We need to let them finish their work. These are expert people. They'll get to the bottom it and then we'll let all of you know what they find out. Dreamliner woes explained