Private William McWhirter, son of Charles and Jemima McWhirter, of Ruthwell, served with 7th (Airborne) Battalion, King's Own Scottish Borderers.In early 1944, numerous training exercises were being undertaken in preparation for the Allied invasion of North-West Europe that year. On 4 April 1944, 1 HGSU, Horsa I LG999 took part in a large glider exercise (codenamed 'Exercise Dreme') towed by Stirling IV LJ842 of No. 196 Squadron. The glider occupants were two glider pilots and members of No.3 Platoon 'A' Company, 7th (Airborne) Battalion, The King's Own Scottish Borderers.

As the towing aircraft descended through cloud, it hit a tree and 15 minutes later stalled, possibly due a failure of the port outer engine, and crashed. All 27 men onboard Horsa LG999 were killed, including Private William McWhirter, a glider troop passenger.

Private McWhirter died on 4 April 1944, aged 22 years old. He is now buried at Ruthwell Parish Churchyard, Dumfriesshire.