By Dan Catchpole
EVERETT, Feb 3 (Reuters) - Boeing BA.N plans the first flight of a production 777X in April, a company document seen by Reuters shows, an important signal of progress for the planemaker's long-delayed new jet, which is slated for first delivery next year.
The company is conducting fuel tests on the 777X ordered by Lufthansa at Paine Field in Everett, Washington, where it assembles the mini-jumbo, ahead of engine tests later this month, according to the document.
The plane was seen at one of Boeing's fuel docks at Paine Field by a Reuters reporter on Tuesday.
Boeing has taken $15 billion in charges on the development program, which is six years behind schedule.
The 777X test plane fleet has logged more flight hours than any other Boeing program, but the planemaker is still trying to get the Federal Aviation Administration to certify the aircraft. Certification requirements include testing using a production airplane configured as if ready for delivery.
"In addition to the dedicated flight test fleet, some production airplanes will support testing that does not require flight-test unique equipment and instrumentation," a Boeing spokesperson said. The company declined to comment on plans for the specific aircraft or the document.
Lufthansa ordered the plane, a 777-9, in 2013, the year Boeing launched the 777X, according to aviation data analytics firm Cirium.
The 777X is the successor to both the 747 and 777, two of Boeing's most successful jets, and complements the smaller 787 Dreamliner. Together, they make up Boeing's widebody products for long-haul travel. The U.S. company long dominated that market, but it has faced increasingly tough competition from European rival Airbus.
Last week, Boeing CEO Kelly Ortberg disclosed a potential new issue with the 777X's engines made by GE Aerospace GE.N. However, it is not expected to change the company's plan to deliver the first 777X next year.
(Reporting by Dan Catchpole in Seattle; editing by Peter Henderson and Shri Navaratnam)
((dan.catchpole@thomsonreuters.com; 651-231-1623))