Flying became even safer this week; or at least it should have. Thirty-one years ago, the worst accident in the history of civil aviation took place at Los Rodeos airport in northern Tenerife. A bomb attack at Las Palmas, on Gran Canaria, had caused a number of aircraft to divert to Tenerife. Among them were Boeing 747s belonging to KLM and Pan Am. Fog sharply reduced visibility. The pilot of the Dutch plane was keen to get his passengers away, but a mix-up between him, the Pan Am captain and the air-traffic controller meant that he took off while the Pan Am jet was on the runway. All the KLM passengers and crew died, along with most of those on board the American aircraft; in total, 583 perished.