[On this date in 1970 Pan Am’s Clipper Maid of the Seas entered into service. The immediately following paragraph is from an article in 2000 on The Guardian website, the second two are from the Wikipedia article Pan Am Flight 103:]
The Maid of the Seas had been put into service on 12 February 1970 and had since made 16,497 flights and logged in 72,646 flight hours. But, in spite of the age of the machine, the pilots had no reason to worry as they made their final checks.
The aircraft operating Pan Am Flight 103 was a Boeing 747–121, registered N739PA and named Clipper Maid of the Seas, formerly named Clipper Morning Light prior to 1979. It was the 15th 747 built and was delivered in February 1970, one month after the first 747 entered service with Pan Am.
At the time of its destruction, Clipper Maid of the Seas was 18 years of age and had accumulated over 75,000 flying hours. In 1987, it underwent a complete overhaul as it belonged to the civil reserve fleet of aircraft and this aircraft was retrofitted so that, in a national emergency, it could be turned into a freight aircraft within two days' work, according to the Los Angeles Times.