"That meant a survey of each airframe - no small task".
But, individually - not that big a task either. Remember, the Viking T.1 is not a Hawk T.1. It's a sailplane that doesn't even have flaps, and the U/C is fixed. Was it really that difficult to look at the records of each aircraft, and starting with the ones that had never been pranged de-rig each one, take a really good look at it and then release it to service? Surely after 18 months that would've provided the ATC with at least some serviceable aircraft?