cycles. by the date of the crash, this particular 747 has already gone more than 12,000 cycles. the repair is inspected but because of a sealant has been used over the gap in the bulkhead, cracks developing between the rivets are not found. this plane is a ticking time bomb. unfortunately the repair was insufficient and cracks started to develop over the service life after the airplane was returned into passenger use. there was no proper inspection procedure as well. reporter: as jal 123 passes through 24,000 foot, cracks begin to connect between the rift leading the bulkhead to fail cat strofcally. it is a structural failure due not to bad airplane design but to a faulty repair and inadequate oversight. when we look back at structural failures how common is it that it is repair related