UPDATE 1-Boeing 787's dimmable windows not dark enough, says ANA

* ANA asks Boeing to find way to make windows darker

* ANA may install blinds on two long-haul 787s

* ANA says 787 saved 21 pct on fuel on long haul flights

By Tim Kelly

TOKYO, June 20 (Reuters) - Boeing Co's launch customer for its 787 Dreamliner, Japan's All Nippon Airways says the plane's electronic dimmable windows are not dark enough for long haul flights and has asked the U.S. aircraft maker to come up with a way to make the plane's cabin darker.

The Japanese airline is looking to install pull down blinds on 787s already delivered, an industry source with knowledge of the matter told Reuters. ANA wants darker windows for two Dreamliners operated on long haul routes, company spokesman Ryosei Nomura said.

"For our passengers to have good sleep, we realised that it is important to offer appropriate darkness during flights especially for long haul," Nomura said.

ANA has ordered 55 787s, a replacement for the 767, making the new jetliner the centerpiece of its fleet plans for the next several years. The carbon composite plane is designed to be more fuel efficient and, therefore, cheaper to operate. It also boast higher cabin pressure and humidity in order to make flying more comfortable.

The 20 percent larger than standard dimmable windows, the first on a commercial passenger jet, darken but do not go opaque.

The U.S. planemaker declined to say whether other 787 customers had asked for darker windows or to discuss how it would meet ANA's request.

"Specific discussions between Boeing and our customers are considered proprietary and we cannot comment on them," Rob Henderson, a Boeing spokesman in Tokyo, said. "The response of our customers and the flying public to the larger, dimmable windows on the 787 has been very favourable," he added

Boeing so far has taken more than 850 orders for its 787, and says it will crank up production to 10 aircraft a month by the end of 2013. Glitches such as recent signs of delamination on the rear fuselage of some planes will not, it insists, further delay a project three years behind schedule. Delamination occurs when stress causes layered composite materials to separate.

ANA's local rival Japan Airlines is also a big customer for the 787, with four already flying international routes and another 41 of the jets on order. The carrier said so far it has not asked Boeing for darker windows.

"At this moment, we have not made any such request to Boeing," JAL spokeswoman, Sze Hunn Yap said.

The U.S. company accounts for around 90 percent of commercial plane sales in Japan, the biggest market share it has in any major aviation market.

Apart from the windows, ANA says it is happy with the seven 787s it operates. In the first six months of flying the aircraft on international routes, the plane burned 21 percent less fuel compared with a 767, the carrier said. Boeing's sales pitch claims a 20 percent fuel savings.

ANA added that a survey of passengers found that nine out of 10 said the plane met or exceeded their expectations.

ANA shares, which have gained 7 percent this year compared with a 2.5 percent gain in the benchmark Topix index in Tokyo, rose 3.6 percent to close at 231 yen on Wednesday.