A look at the hybrid military aircraft involved in Hawaii crash that killed 1, injured 21

HONOLULU — An investigation is underway after a U.S. military Osprey aircraft crashed during a weekend training exercise in Hawaii, killing a Marine and injuring 21 others.

Here are some things to know about the hybrid aircraft:

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HELICOPTER OR PLANE?

It's actually both. The Osprey is a tilt-rotor aircraft, which means its propellers can be adjusted to fly either vertically or horizontally. That allows it to take off and land vertically like a helicopter, but it also flies like a fixed wing airplane.

It can reach up to 277 mph and 25,000 feet, making it ideal for long-range missions.

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Ospreys are used by the Marines and Air Force, and have been deployed to the wars in Iraq and Afghanistan.

Air Force Special Operations forces use Ospreys for especially risky missions like going behind enemy lines at low altitude at night, said Loren Thompson, analyst at the Lexington Institute, a defense-oriented public policy advocacy group. The Marines normally wouldn't use the aircraft for such missions, Thompson said.

Some Ospreys are involved in humanitarian work, such as assisting earthquake relief efforts in Nepal. The aircraft also have been used to deliver supplies to those fighting Ebola in Liberia, and aid to typhoon victims in the Philippines.

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SAFETY RECORD

There were two crashes of its initial version, in 1991 and 1992. Seven people died in the second wreck.

In 2000, two test crashes killed 23 marines. In 2010, three service members and a civilian contractor were killed in a wreck of the Air Force version of the aircraft.

The Osprey's track record has since greatly improved. The military maintains the aircraft are safe, and the Hawaii training exercises continued after the crash.

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JAPAN'S CONCERNS

The U.S. military already has 24 Ospreys on Okinawa, and last week said 10 more would be stationed at Yokota Air Base near Tokyo, starting in 2017.