On August 1, 2014, a Qantas plane struck the tarmac with its tail during its takeoff maneuvers at the Sydney airport, according to the Australian Transport Safety Bureau (ATSB).

The pilots inserted the aircraft's weight erroneously into the on-board iPad, causing the software to miscalculate the necessary lift-off speed. This translated into the plane rotating and scraping the runway with its tail during take-off.

On November 16, 2015, authorities finally released a report that sheds light upon the incident. Based on the report, the two pilots underestimated the weight of the plane by 10 tons (20,000 lbs). The pilot stated that the weight of 66.4 tons (132,800 lbs) they introduced was in line with the values from recent flights, so he didn't think twice about the value.

The Boeing 737 plane flying to Darwin had 152 passengers on board and weighed 76.4 tons (152,800 lbs). Crew cabin members reported to the captain about hearing a "squeak" during take-off, but the dedicated sensors on the aircraft's tail stayed silent.  

Both engine thrust and takeoff speed are lower for a lighter aircraft. At what was supposed to be the optimal lift-off speed, the sub-throttled aircraft tilted backward and gently touched the runway with its tail.

At an inspection of the plane at the Darwin airport, the main pilot noticed some marks under his aircraft's tail, a sign that a tail scrape took place.

"The ATSB found the tailstrike was the result of two independent and inadvertent data entry errors in calculating the take-off performance data," the report confirmed.

Qantas Airlines offered to reevaluate its pre-flight safety procedures and promised to update the operating manual for the flight crew, so incidents of this sort can be avoided.

One way to do so is to have an independent cross check which evaluates the take-off weight. Corroborating this info with the one in the final load sheet should make tail-strikes a thing of the past.

Another mention in the reports acknowledged human error, which traffic safety authorities note as something independent of the pilot's experience.

"Data input errors can occur irrespective of pilot experience, operator, aircraft type, location or take-off performance calculation method," the report reads.

There is hope that proper communication, independent cross-checks and effective management will eliminate mistakes in the future.   

On what seems to be an ironic plot twist, the Australian airline celebrated 95 years since its first flight when ATSB's report appeared.