There was no evidence to suggest that the fact that both tyres had been retreaded 3 times was a factor in the failure occurrence. This type of aircraft tyre (Type VII) is routinely retreaded 6 times or more before being taken out of service. The criteria for final rejection for retreading, except for severe cuts or impact damage, is advanced carcass structural deterioration. Such structural deterioration, symptomised by propagating interply separation, should be evaluated at each retread level, by the retreader, using nondestructive testing methods such as Air Needle and/or Holography techniques. Detailed visual examinations of the delaminated ply surfaces on the tyre remnants revealed no evidence of previous internal separations. There were also no indications of ply separation at the old and new tread interface on either tyre.