The fatality rate on passenger jet aircraft worldwide jumped in 2018 after airlines recorded zero accident deaths on passenger jets in the prior year, according to a Dutch consulting firm and an aviation safety group.

Dutch aviation consulting firm To70 and the Aviation Safety Network both reported on Tuesday there were more than 500 deaths stemming from passenger airline crashes in 2018, but emphasized that fatal crashes remain rare.

To70 estimated that the fatal accident rate for large commercial passenger flights at 0.36 per million flights, or one fatal accident for every 3 million flights.

That is up from 2017’s 0.06 per million flight rate and above the most recent five-year average of 0.24 per million flights. There were 13 deaths in 2017 in two fatal crashes worldwide, but both were on regional turboprop aircraft.

Over the last two decades, aviation deaths around the world have been falling. As recently as 2005, there were 1,015 deaths aboard commercial passenger flights worldwide, the Aviation Safety Network said.

Despite the increase, 2018 was still the third safest year ever in terms of the number of fatal accidents and the ninth safest measured by deaths, the Aviation Safety Network said.

“If the accident rate had remained the same as ten years ago, there would have been 39 fatal accidents last year,” Aviation Safety Network’s chief executive, Harro Ranter, said in a statement. “This shows the enormous progress in terms of safety in the past two decades.”

On Oct 29, a Lion Air-operated Boeing 737 MAX 8 crashed into the Java Sea after takeoff from Jakarta, killing 189.

In May, a Cubana flight of a Boeing 737-201 crashed just outside Havana airport, killing 112 people. In March, 51 of 71 on board died after a US-Bangla Airlines plane crashed on landing at Nepal’s international airport.

In February, a plane operated by Saratov Airlines crashed in Russia after taking off from Stepanovskoye, killing all 71 people aboard, while the same month an Aseman Airlines flight crashed into a mountain in Iran, killing 66 people onboard.

The United States suffered its first accident death involving a U.S. airline since 2009 in April, when a fan blade on a Southwest Airlines Co (LUV.N) Boeing 737’s jet engine broke apart in flight, shattering a window and nearly sucking a woman out of the plane.