Boeing's maintenance teams started modification works on All Nippon Airways (ANA) and Japan Airlines' (JAL) Boeing 787s on the morning of 22 April.
ANA has five Boeing teams at four airports across Japan, each working on a 787 aircraft. Two of these teams are at Tokyo's Haneda airport, where ANA has 10 787s, while the other three teams are each at Narita, Matsuyama and Okayama airports, where ANA has another four 787s in total.
The work on another three ANA 787s, one each in Kumamoto, Takamatsu and Frankfurt, is expected to start in May, says an ANA spokesman.
The Boeing teams, which have been on standby in Japan since early April, will be installing containment and venting systems for the main and auxiliary system batteries. They will also replace the batteries and their chargers with modified components, he adds.
Each team is expected to take five days to modify one aircraft.
"Since we have 17 787s, it should take a month to finish all the modifications on our aircraft," says the ANA spokesman.
Boeing has, meanwhile, dispatched two maintenance teams to JAL - one at Narita airport and the other at Haneda airport. Out of the carrier's seven 787-8s, five are in Narita, one in Haneda and another in Boston.
"We expect it to take several weeks to complete the modifications. We will then have to wait for the Japan Civil Aviation Bureau [JCAB] to issue the directive to lift the ban on 787, then we can decide when to return them to service," says a JAL spokesman.
The US Federal Aviation Administration is expected to issue a new airworthiness directive to supersede the order that grounded the 787s, made in January, during the week ending 28 April. The JCAB is likely issue a similar directive in Japan shortly after.
Both Japanese carriers declined to say when their 787s will likely return to service.
Since earlier this month, ANA has started offering domestic 787 tickets from 1 June. At the start of April, the carrier also started simulator training for its 180 787 pilots to prepare them for the resumption of 787 operations after more than a three-month break.
ANA could not say how many hours the pilots would need to clock on the 787s, or how many round trip test flights it would conduct, before the aircraft are put back in operations.
The US FAA, on 19 April, approved Boeing's solution to the thermal and electrical failures that caused the lithium-ion batteries on two 787s to dangerously overheat. Boeing has deployed teams worldwide to begin the installation of the improved battery on the 787s that were in service before the grounding. The aircraft will be modified in around the same order as they were delivered.
ANA and JAL are the world's largest operators of the 787. Flightglobal Pro data shows that ANA has received 17 787-8s, with an additional 19 -8s and 30 787-9s on order. JAL, meanwhile, has seven -8s in its fleet, with an additional 18 -8s and 20 787-9s on order.