On a cold winter’s night in 2001, an Iberia A320 flying from Barcelona to Bilbao encountered a new phenomenon just before touchdown, which threatened the safety of all 136 passengers and 7 crew.

It happened on Friday, Feb. 21, an Iberia Airbus A320, traveling from Düsseldorf Airport in Germany to Barajas Airport in Madrid. The flight crew described the spider as a tarantula. The pilot ...