WASHINGTON -- There were no commercial passenger jet deaths anywhere in the world last year. It's a remarkable record, but one that has been building for some time.

Global and U.S. commercial aviation deaths have been trending downward for more than a decade due to a variety of factors.

The Dutch aviation consultancy To70 and the Aviation Safety Network reported Monday about the numbers from last year, although there were two fatal regional airline crashes involving small turboprop planes in Angola and Russia. There also were fatal accidents involving cargo airliners.

Much of the credit for reducing passenger airline deaths goes to aircraft safety systems that virtually have eliminated midair collisions between airliners and what is referred to in aviation as "controlled flight into terrain." Usually that means flying a plane into the side of a mountain.

There have been other improvements as well, including airlines adopting safety programs designed to spot potential problems before an accident occurs rather than relying on learning lessons from analysis after a crash.

Fang Liu, secretary general of the International Civil Aviation Organization, a U.N. agency that sets international safety standards, said in a statement the 2017 results reflect the "commitment and cooperation" of many governments, airline companies and aviation professionals worldwide "who have worked so hard together to achieve them."

In the U.S., it has been 4 1/2 years since the last deaths involving a scheduled passenger airline. Three passengers died after Asiana Airlines Flight 214 crashed while landing at San Francisco International Airport on July 6, 2013.

It's been almost nine years since the last fatalities involving a U.S.-registered, scheduled passenger airline in the United States. That was Colgan Air Flight 3407, which crashed on approach to Buffalo, New York, on Feb. 12, 2009. All 49 people on board and a man on the ground were killed. Colgan, now defunct, was a regional airline.