* Japan, U.S. approve resuming Dreamliner flights
* ANA to fly 230 test flights before commercial flights
* JAL sees test flights in May, commercial flights June
* Boeing to hold news conference on Saturday at 0200 GMT
By Tim Kelly and Mari Saito
TOKYO, April 26 (Reuters) - Japan's All Nippon Airways will conduct a test flight of Boeing Co's 787 Dreamliner on Sunday, as it prepares to bring back passengers on a plane that was grounded across the world following incidents of batteries overheating.
The test flight by ANA, the Dreamliner's top customer, comes after U.S. and Japanese authorities gave approval for flights to resume and will be the first of some 230 flights the airline has planned before allowing the jet to carry passengers.
Boeing Commercial Airplanes Chief Executive Ray Connor and ANA Group CEO Shinichiro Ito will be on board Sunday's flight.
ANA has yet to decide when commercial flights would restart, President Osamu Shinobe said, but he reiterated the Dreamliner would remain a core part of its fleet strategy.
"I believe that safety has been secured now, but only by flying the 787 smoothly will we be able to demonstrate its safety and reassure our passengers," Hiroyuki Ito, ANA senior executive vice president, told reporters.
Local rival Japan Airlines Co Ltd said it would start its own test programme from May with the aim of using the jets to carry passengers again from June.
"We have had this trouble with the 787, but it is a great aircraft," JAL President Yoshiharu Ueki told reporters. JAL has seven Dreamliner planes.
On Saturday, Boeing will hold a news conference in Tokyo. Mike Sinnett, Boeing's chief project engineer for the 787, is scheduled to brief media.
Ethiopian Airlines is set to become the world's first carrier to resume flying the Dreamliner, with a commercial flight on Saturday to neighbouring Kenya, two airline sources told Reuters on Wednesday.
ANA, which has 17 Dreamliner jets, has not said how much the grounding has cost the company, though it has said it was losing $868,300 in revenue per plane in the last two weeks of January.
ANA will renew compensation talks with Boeing after it resumes commercial flights and is able to calculate total losses, the company said.
In addition to the battery fix approved by U.S. authorities, Japan's Civil Aviation Bureau has requested airlines meet the country's own safety standards when flying the 787, which include monitoring the battery current while the jet is in the air and checking used batteries.
Teams of Boeing engineers began installing reinforced batteries on Dreamliners owned by ANA on Monday. The airline hopes to complete retrofitting its entire fleet by mid-May.