The CH-53E Super Stallion (search) is a Marine Corps workhorse that requires a lot of care and attention to stay in the sky.

Marine officials said one of the helicopters went down in bad weather Wednesday in western Iraq, killing 30 Marines and a sailor. It was the greatest loss of life for the Marines since the 1983 bombing of a Marine barracks in Beirut (search), Lebanon, that killed 241 people, including 220 Marines.

Officials did not describe what weather may have brought it down, but NASA satellite photos of the region suggested western Iraq was facing dust or sandstorms.

"It's a dangerous environment that we operate in in Iraq, we all understand that," said Army Gen. John Abizaid (search), who was testifying on Capitol Hill.

The helicopter, the largest in the U.S. military inventory, is used to haul heavy cargo or dozens of troops. It has seen action around the world.

But the military plans to replace the Super Stallion with a helicopter that is easier to maintain, said John Milliman, a spokesman for the Naval Air Systems Command. For every hour the Super Stallion flies, it requires 44 man-hours of maintenance, he said.

Built by Connecticut-based Sikorsky Aircraft Corp., the three-engine helicopter cost $39 million apiece when the last one was delivered in 2003. It costs $14,000 an hour to fly, Milliman said.

The Super Stallion is operated by a crew of three and can be configured to carry as many as 55 people.

Before Wednesday, the Marines had 151 CH-53Es, he said. The average CH-53E in the Marines' inventory is almost 16 years old; the oldest in the fleet was built in 1980, the newest, in 1999.

It is a variant of a Vietnam War-era design. The Marines also fly an older model, the CH-53D, which is slated to be replaced by the V-22 Osprey tiltrotor aircraft. The Navy flies the MH-53, a variant suited for minesweeping, and the Air Force flies a special-operations model.

The CH-53Es were temporarily grounded in 1996 and again in 2000 after crashes.

"It's an awfully big helicopter. It's got a lot of things on it that can break," said John Pike, a military expert at globalsecurity.org. "The thing has had safety problems."

Military officials said the CH-53's safety record is on par with other Marine Corps aircraft. Over the past five years, Marine aircraft, both planes and helicopters suffered an average of 3.21 major accidents for every 100,000 hours in the sky. Since 1981, CH-53s have suffered 35 such accidents -- defined as causing $1 million or more damage -- a rate of 3.22 major accidents per 100,000 flying hours.

Military officials said the CH-53s safety record is on par with other Marine Corps aircraft. Over the last five years, Marine aircraft, both planes and helicopters, suffered an average of 3.21 major accidents for every 100,000 hours in the sky. Since 1981, CH-53s have suffered 35 such accidents -- defined as causing $1 million or more damage -- a rate of 3.22 major accidents per 100,000 flying hours.

In some other incidents:

-- On Tuesday, a Navy MH-53E Sea Dragon ditched in the Atlantic off the coast of Virginia, officials said. All eight people on board were rescued.

-- On Aug. 13, 2004, two Marines were killed when a CH-53 crashed in Anbar province. The cause of the crash is unclear. Officials said at the time no enemy fire was seen.

-- A German CH-53 crashed in Afghanistan in December 2002, killing seven. The crash was blamed on a faulty reassembly of the helicopter after it was shipped to the war zone.

-- On Jan. 20, 2002, two Marines were killed when their Super Stallion helicopter crashed while on a resupply mission in Afghanistan. Five other Marines injured.

Although most of the U.S. military deaths in Iraq have come during ground fighting and ambushes, some of the most spectacular and deadly incidents since the U.S.-led invasion have involved helicopters.

On Nov. 15, 2003, two Army UH-60 Black Hawks crashed in Mosul, killing 17 soldiers and injuring five. The military said the helicopters collided during what was probably a rocket-propelled grenade attack. On Nov. 2, a CH-47 Chinook transport helicopter was shot down near Fallujah, killing 16 and injuring 26. The military believed a SA-7 shoulder-fired missile struck an engine.