WASHINGTON -- There were more airline deaths worldwide due to deliberate acts in 2015 than from accidental air crashes, for the second year in a row, according to an industry tally.

There were only eight accidental airline crashes last year, accounting for 161 passenger and crew deaths - the fewest crashes and deaths since at least 1946. The tally by Flightglobal, an aviation news and industry data company, excludes a German airliner that was deliberately flown into a mountainside in the French Alps last March, and a Russian airliner packed with tourists that exploded over Egypt in October. The toll for those two incidents was 374 killed.

In 2014, the toll from a Malaysia Airlines plane that disappeared and another that was shot down over Ukraine in 2014 was 537 deaths compared to 436 accident deaths that year.

"In recent years, airline safety has improved very considerably to the point where, typically, there are now very few fatal accidents and fatalities in a year," said Paul Hayes, Flightglobal's director of air safety and insurance. "However, flight security remains a concern."

Although some years are better than others, the fatal accident rate has been improving for many years. The global fatal accident rate for all types of airline operations in 2015 was one per 5 million flights, the best year ever. The previous best year was 2014, with a fatal accident rate of 1 per 2.5 million flights. Airline operations are now about four or five times safer than they were 20 years ago.

Those tallies are for all types of airline flights, including cargo, positioning, training, and maintenance flights. There were just 98 paying passengers killed last year in accidental crashes compared to 790 in 2007. A far cry from 1970s, when the annual average of passengers killed in accidental crashes was 1,289.

A big reason for the improving record is better engineering: Today's airliners and aircraft engines are far safer than earlier generations of planes. They are more highly automated, which has reduced many common pilot errors. They have better satellite-based navigation systems. They are made of stronger, lighter weight, less corrosive materials. And they're equipped with safety systems introduced in recent decades, and repeatedly improved over time, that have nearly eliminated mid-air collisions between airliners and what the industry calls "controlled flight into terrain" - pilots who lose situational awareness and fly their planes into a mountainside or into the ground.

The aircraft improvements are due primarily to lessons learned from crash investigations that are taken into account when new planes are designed, said John Goglia, a former National Transportation Safety Board member. As older planes are replaced with newer planes, aviation becomes safer, he said.

"We're now up to about the 7th generation of jet airplanes," he said. "We know the first generation - DC-8s, 707s - had a higher accident rate than the second or the third or the fourth generations, and it just moves on up."

But more needs to be done to weed out disturbed pilots and guard against acts of terrorism, experts said.

The Germanwings case is especially perplexing, said John Cox, a former airline pilot and aviation safety consultant. Pilot Andreas Lubitz managed to conceal his troubles even though airlines are continually evaluating pilots for signs of trouble. Pilots evaluate each other as well.

It's not known what caused Malaysia Airlines Flight 370 to disappear while flying from Kuala Lumpur to Beijing, but many aviation safety experts theorize that it was mostly likely the result of deliberate acts, probably by one of the two pilots.

"Pilots from day one are so ingrained with protecting the passengers, with learning skills to deal with unanticipated events ... and evaluated on how well you deal with stress," Cox said. "Those who don't do well with it don't survive as professional pilots."

The Islamic State has claimed credit for a bomb suspected of blowing apart a MetroJet A320 over Egypt. Malaysia Airlines Flight 17 was shot down by a Russian Buk surface-to-air missile fired from rebel-held territory in Eastern Ukraine, according to Dutch crash investigators.

Terrorists "have been probing nonstop since 9/11 and every once in a while they find a way to get through," Goglia said.

The new frontier in airline safety is a managerial philosophy known as SMS, or safety management systems, he said. Airlines are systematically gathering data on safety trends, and encouraging pilots, dispatchers, mechanics and others to report problems by promising there will be no retaliation for mistakes. The information is then shared across the industry in an effort to spot problems before they lead to an accident.