A software error resulted in an airliner not having enough runway to abort take off, investigators said.
Some 156 passengers and six crew were on board the Airbus A319-111 when it departed from Belfast International Airport.
When the captain of the plane saw the end of the runway, he "felt that a rejected take off would not provide sufficient stopping distance", a report by the Air Accidents Investigation Branch (AAIB) stated.
The pilot therefore decided that he would not reject the take off and the aircraft became airborne with around 200 metres (219 yards) of runway remaining, the AAIB added.
Investigators concluded that the incident on June 25 last year was caused by incorrect take off data after an "anomaly" with the Airbus FlySmart software on the captain's PC led to a change in runway choice.
The captain and his co-pilot confirmed that they had selected the correct option, but the take off calculations provided by the computer were made using a runway which is over 1,000 metres (1,093 yards) longer than the one actually used.
The AAIB stated: "The potential seriousness of the event is highlighted by the theoretical result of a runway overrun."
A number of international organisations are currently assessing the risk of using incorrect take off data.