Image caption An ANA Dreamliner flight had to make an emergency landing in January after battery problems

Japan's All Nippon Airways (ANA) has said it will cancel all Boeing 787 flights until at least the end of May, in the latest blow to Boeing.

International regulators grounded all 787 Dreamliners in January so that safety checks could be carried out on their lithium ion batteries.

ANA is cancelling more than 1,700 flights in April and May, a period that includes Japan's Golden Week holiday.

It takes the total number of affected ANA Dreamliner flights to 3,600.

ANA is Boeing's biggest Dreamliner customer, with 17 of the world's 50 operational 787s.

Referring to the extended period of cancellations, an ANA spokeswoman said: "Unfortunately, it includes Golden Week, but we have decided to inform our customers in advance as the prospect for their resumption is still unseen."

Proposed fix

Boeing's entire fleet of Dreamliners was grounded after a battery on a Japan Airlines 787 caught fire, and a malfunction forced an ANA flight to make an emergency landing.

But investigations into the battery have so far proved inconclusive.

On Friday, Boeing gave US regulator, the Federal Aviation Administration (FAA), its plan to fix the battery problems, which reportedly involves a significant redesign of the battery pack with new ceramic insulation around each of the battery's eight cells.

According to the Seattle Times, the fix also involves using a system of venting tubes that in case of an incident would channel any flammable vapours or liquids directly out of the plane, and continuous monitoring of the temperature and voltage of individual cells within the battery.

The FAA said it was reviewing the plan. "The safety of the flying public is our top priority and we won't allow the 787 to return to commercial service until we're confident that any proposed solution has addressed the battery failure risks," it said.

Boeing hopes the fix could allow Dreamliners to be back flying by mid-April. But industry analysts have suggested it could take longer, as getting approval for the redesigned batteries could take several months.

"Recertification suggests time,'' Carter Leake, an aerospace analyst at BB&T Capital Markets, said.

"Given what most know about aircraft certification processes, six months would be sort of quick.''

Financial damage

The problems with the Dreamliner are already proving costly to airlines and to Boeing, and the costs are set to continue growing.

ANA lost some 1.4bn yen ($15m; £9.5m) in revenue through January's disruption alone.

Boeing also faces potential compensation payouts to airlines who have been forced to cancel Dreamliner flights.

Last week, Australian carrier Qantas said it had received 125m Australian dollars ($129m; £85m) compensation from the US planemaker over the grounded 787s.

Analysts have also warned that Boeing's woes could deepen if airlines who have the Dreamliner on order ask for deliveries of the plane to be delayed.

The planemaker itself has already had to delay delivery of the plane to two European airlines - Thomson Airways and Norwegian Air Shuttle.

Thomson, which had been due to take delivery of Dreamliners at the end of February, said it had not yet been given a new delivery date by Boeing.

"Our priority is to ensure our customers go on their holidays and we are, therefore, putting contingency plans in place including using alternative aircraft for our long-haul flights to Mexico and Florida if delivery is delayed beyond the end of March," Thomson said in a statement.