The number of air accidents and resulting fatalities dropped in 2015 from the previous year, and was well below the five-year average, the International Air Transport Association (Iata) said on Monday.

Some 68 accidents occurred last year, compared with 77 in 2014 and an annual average of 90 over the last five years, according to Iata's latest annual report on aviation safety. Of 2015's accidents, four were fatal, versus 12 a year earlier.

"In terms of the number of fatal accidents, it was an extraordinarily safe year," Tony Tyler, Iata's director general and chief executive officer, said in a statement.

The accidents covered by the report killed 136 people, down from 641 in 2014 and a five-year average of 504, according to Iata, which represents some 260 airlines or 83 percent of the world's total air traffic.

If the losses of aircraft in incidents involving planes operated by German low-cost carrier Germanwings, a unit of Deutsche Lufthansa AG, and Russia's Metrojet last year are included, the total number of deaths rose to 510, according to Iata.

But the Germanwings and Metrojet incidents were excluded from Iata's accident statistics, as they were classified as deliberate acts of unlawful interference. A pilot of the Germanwings aircraft deliberately crashed that plane in the French Alps, while the Metrojet flight was suspected to have been brought down over the Sinai peninsula by a bomb smuggled on board.

"While there are no easy solutions to the mental health and security issues that were exposed in these tragedies, aviation continues to work to minimise the risk that such events will happen again," said Tyler.

Iata said the 2015 global jet accident rate, measured in hull losses per 1 million flights, was 0.32, compared with 0.27 in 2014 and 0.46 in the previous five years. - Reuters