A professor of aerospace engineering explains.
It's thought the bolts were removed to fix rivets damaged in the production process.
It's the latest blow to Boeing's reputation.
The new scanning machines remove the need for physical bag searches in most cases.
The plane was built in Oklahoma, USA, in 1945.
"This is exciting for New Zealand."
The aircraft went down at the Omaka Aerodrome in Blenheim, killing the pilot.
Police will refer this incident to the Civil Aviation Authority.