A bomb explodes on board Pan Am Flight 103 over Lockerbie, Dumfries and Galloway, Scotland, killing 270. This is to date the deadliest air disaster to occur on British soil.

Pan Am Flight 103 was a regularly scheduled Pan Am transatlantic flight from Frankfurt to Detroit via a stopover in London and another in New York City. Shortly after 19:00 on 21 December 1988, the Boeing 747 "Clipper Maid of the Seas" was destroyed by a bomb while flying over the Scottish town of Lockerbie, killing all 243 passengers and 16 crew aboard. Large sections of the aircraft crashed in a residential street in Lockerbie, killing 11 residents. With a total of 270 fatalities, the event, which became known as the Lockerbie bombing, is the deadliest terrorist attack in the history of the United Kingdom.

Lockerbie is a town in Dumfries and Galloway, located in south-western Scotland. The 2001 Census recorded its population as 4,009. The town had an estimated population of 4,190 in 2020. The town came to international attention in December 1988 when the wreckage of Pan Am Flight 103 crashed there following a terrorist bomb attack aboard the flight.

Dumfries and Galloway is one of the 32 unitary council areas of Scotland, located in the western part of the Southern Uplands. It is bordered by East Ayrshire, South Ayrshire, and South Lanarkshire to the north; Scottish Borders to the north-east; the English county of Cumbria, the Solway Firth, and the Irish Sea to the south, and the North Channel to the west. The administrative centre and largest settlement is the town of Dumfries. The second largest town is Stranraer, located 76 miles (122 km) to the west of Dumfries on the North Channel coast.

December 21 is the 355th day of the year in the Gregorian calendar; 10 days remain until the end of the year.