Recertification will be even more challenging than procedure outlined by Helix Von Smelix #1312 because the standard is statistical risk, not absolute. NTSB quantified the risk requirement; “Boeing .....determined that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours”. In real life “there have been two critical battery events on the 787 fleet with fewer than 100,000 flight hours”. In fact fleet hours were only 52,000 so Boeing must substantiate to a critical audience that improvements to the battery system yield at least a 200 fold reduction in risk of failure.