The reliability of Boeing's pioneering 787 Dreamliner jet is improving but is still not satisfactory, the planemaker's top official in charge of keeping the jet flying said on Friday.
The Dreamliner's reliability rate is now around 98 percent, meaning two out of every 100 flights are delayed for mechanical problems - up from 97 percent in October but still short of the firm's target, said Mike Fleming, vice president for 787 support and services.
He was speaking at a news conference in Oslo where Norwegian Air Shuttle ASA, one of the jet's most publicly critical customers, has faced a series of glitches.
"I'll tell you that's not where we want the airplane to be, we're not satisfied with that reliability level of the airplane," Fleming said.
"The 777 today flies at 99.4 percent ... and that's the benchmark that the 787 needs to attain.
"We introduced the 777 in 1995 and it was in the 1999 timeframe that we saw sustained performance over 99 percent in that fleet ... to get the fleet above 99 percent you have to keep working every day, so my guess is that it will be similar to what we had with the 777," he added.
Norwegian Air Shuttle, the only European budget carrier to fly long haul, has been plagued by problems with its first three Dreamliners, with a series of breakdowns last year leaving passengers stranded.
The Dreamliner was supposed to be a game-changer for the aviation industry as its lighter body and electrical systems cut fuel consumption by 20 percent and reduced maintenance.
But it has been beset by problems including a battery fire that grounded all 787s in service for three months last year and forced Boeing to re-design the powerful lithium-ion battery and enclose it in a tough new steel containment box.
It also equipped the battery with a metal exhaust tube to vent fumes and gases outside the jet if the battery were to overheat.
Earlier this month, a Japan Airlines maintenance crew noticed white smoke coming from the main battery of a Dreamliner, with a cell found to be showing signs of melting just two hours before the plane was due to fly.
"We recently had a single-cell failure in a battery on another customer's airplane and we didn't get propagation of that to other cells, other cells continued to function," Fleming said. "The containment box worked as supposed to and the vapour vented overboard as supposed to."