No large commercial passenger jets has fatally crashed in 2017, two reports show, making the year the safest in aviation history.

Aviation Safety Network (ASN) estimates that the chances of fatal airliner crash are now one in seven million. It recorded a total of 10 fatal airliner accidents – five cargo and five passenger – and 79 fatalities (44 occupant and 35 on the ground) in 2017. The previous year saw 303 deaths and 16 accidents.

“Since 1997 the average number of airliner accidents has shown a steady and persistent decline, for a great deal thanks to the continuing safety-driven efforts by international aviation organizations such as ICAO, IATA, Flight Safety Foundation and the aviation industry,” said Harro Ranter, ASN President in a statement.

Dutch consulting firm To70 also released an aviation safety report of 2017, providing an even more optimistic estimation of fatal airliner crash possibility – one in sixteen million. The company accounts a total of 111 civil aviation accidents in 2017, two of which were fatal (resulting in 13 deaths). By comparison, it accounted 71 accidents of which six were fatal in 2016.

The difference in numbers provided by the ASN and To70 in this case arises from the difference of the research model. The ASN takes into account the fatal accidents of commercial aircraft – cargo or passenger flights carrying at least 14 passengers.

To70 accounts the accidents of passenger flights by planes with a maximum take-off mass of no less than 5700 kg. It excludes accident numbers of small commuter aeroplanes, military flights, training flights, private flights, cargo operations and helicopters.

Contrary to ASN, To70 attributes the low accident rate to “good fortune” and warns to watch out for factors such as the application of new technologies, maintenance (particularly to the already-arisen ones on the 787 Dreamliner engines) and human factors (e.g. mental health issues and fatigue) in 2018.