Claudel, That is a very interesting point you raised. I always base my records on when an aircraft is delivered to Baldonnel and not on its acceptance date at the manufacturers.There have been a number of instances when the acceptance date is weeks earlier than the delivery to Baldonnel. An example would be the protracted delivery of the first four Seafires. The acceptance flight was on 23 Jan 1947, they took off from Swindon the next day and had to divert to High Ercall and were snowed in until 17 Feb when they flew to Baldonnel.
The Pilatus 260 you mention was delivered in March, but the Swiss regristration was not cancelled until 10 May 2004. I would be very interested to know the date in March for the acceptance, please.
Tony K