On August 1 last year, a Boeing 737-838 (VH-VZR) operated by Qantas performed a "tailstrike" while taking off from Sydney airport. Today, the Australian Transport Safety Bureau (ATSB) has concluded that the strike was caused by the co-pilot fat-fingering the plane's takeoff weight: instead of typing the plane's actual weight of 76,400kg into the iPad, he accidentally typed 66,400kg. As a result, the plane didn't have quite enough thrust to clear the runway without clipping the ground with its tail.
Before you get too panicky, don't worry: this was still very much a human error. The iPad wasn't directly hooked up to the plane; the tailstrike wasn't caused by some software glitch in iOS.
According to the ATSB investigation (PDF), two mishaps occurred "independently and inadvertently." First, when working out the plane's takeoff weight on a notepad, the captain forgot to carry the "1," resulting in an erroneous weight of 66,400kg rather than 76,400kg. Second, the co-pilot made a "transposition error" when carrying out the same calculation on the Qantas on-board performance tool (OPT)—an iPad app for calculating takeoff speed, amongst other things. "Transposition error" is an investigatory euphemism for "he accidentally hit 6 on the keyboard rather than 7."