The US Federal Aviation Administration (FAA) has published a proposed order that will lift the grounding on the Boeing 787 fleet.
The airworthiness directive that will be published on 26 April - on the 100th day of the fleet-wide grounding - will allow the 787 to resume flights after airlines install redesigned lithium-ion batteries and new venting ducts in the aft electrical equipment bay. The FAA estimates that it will cost about $464,000 to complete the modifications on each aircraft, or roughly $23.2 million overall for the 50 787s already delivered.
Boeing also has to modify 25 more 787s that have been assembled after the grounding began on 26 January, raising the total cost to modify the fleet to $34.9 million.
Boeing says it also invested 200,000 labour hours to design and test the redesigned batteries and new venting system on the 787.
The FAA ordered the grounding on 16 January less than 24h after a second lithium ion battery on board a 787 over-heated in less than a 10-day period.
The US National Transportation Safety Board has determined that the battery of a Japan Airlines 787 over-heated after a short circuit developed within one of eight cells. Both the NTSB and the Japan Transportation Safety Board are still investigating why the short circuit developed within the battery cell.