Decades-old contracts signed by an airline in an order for six planes worth more than £5m has been donated to a museum.

Falko Regional Aircraft Limited discovered the contracts, completed with seals, in a two inch-thick folder in its archives.

They were signed by British European Airways which agreed to buy six de Havilland Comets, which were built in the 1960s.

Inside a 60-year-old Comet jet, Falko bosses presented the documents to the de Havilland Aircraft Museum in London Colney last week.

Mike Nevin, the de Havilland Museum’s Marketing Director and Trustee, said he was delighted to receive the rare contracts.

He said: “It is a remarkable document and it has a treasured place in our museum now. It shows the vast amount of detail the contracts have to go into to cover every eventuality.”

The Hatfield-based firm’s chief executive Jeremy Barnes explained how the documentation was discovered.

He said: “The contracts would have been in the de Havilland archives when it became British Aerospace, and was then put into the BAE systems archive and we then inherited it.

“We are having to archive a lot of materials, which go back to the days when we were part of British Aerospace [before the buyout and creation of Falko], and among them was this folder.”

Falko has previously donated a partially dismantled BAE 146 medium haul airliner, nicknamed the whispering jet, to the Salisbury Hall museum.