On the afternoon of March 27, 1977, a bomb threat at Gran Canaria Airport diverted dozens of aircraft to the smaller Los Rodeos airfield on Tenerife in the Canary Islands. Among them were two Boeing 747s: KLM Flight 4805 (PH‑BUF) and Pan American Flight 1736 (N736PA). When Gran Canaria reopened, both aircraft prepared to depart. A dense fog rolled in, reducing visibility to roughly 300 metres. As the KLM crew taxied for takeoff, the Pan Am crew was still on the same runway, searching for an exit in the murk. Through a series of misunderstood radio transmissions, the KLM captain—an esteemed instructor and one of the airline’s most senior pilots—believed he had received takeoff clearance. His flight engineer asked explicitly whether the Pan Am aircraft had cleared the runway; the captain replied with a forceful “Yes.” Thirteen seconds later, the KLM 747 collided with the Pan Am jet. All 248 aboard the KLM aircraft perished; 335 of the 396 aboard the Pan Am flight were killed, leaving only 61 survivors. With 583 fatalities, the disaster remains the deadliest accident in aviation history.