BOAC Flight 777A was a scheduled British Overseas Airways Corporation civilian airline flight from Portela Airport in Lisbon, Portugal to Whitchurch Airport near Bristol, England. On 1 June 1943, the Douglas DC-3 serving the flight was attacked by eight German Junkers Ju 88 fighter planes and crashed into the Bay of Biscay, killing all 17 on board. There were several notable passengers, among them actor Leslie Howard.

One theory suggests that the Germans attacked the aircraft because they believed that British Prime Minister Winston Churchill was aboard; another suggested that it was targeted because several passengers were British spies, including Howard. During the Second World War, British and German civilian aircraft operated from the same facilities at Portela, and Allied and Axis spies watched the incoming and outgoing traffic. The Lisbon–Whitchurch route frequently carried agents and escaped POWs to Britain.

Aircraft flying the Lisbon–Whitchurch route were left unmolested at the beginning of the war, and both Allied and Axis powers respected the neutrality of Portugal. However, in 1942 the air war had begun to heat up over the Bay of Biscay, north of Spain and off the west coast of France; the Douglas DC-3 lost in this attack had survived attacks by Luftwaffe fighters in November 1942 and April 1943.