MADISON, Wis. — The war in Iraq is creating a major — and perhaps deadly — shortage of night vision goggles for civilian pilots who fly medical helicopters in the United States.

The National Transportation Safety Board has encouraged the use of such equipment since 2006 to reduce the risk of deadly nighttime crashes during emergency medical flights. But air ambulance services that fly sick or injured people to hospitals have been put on waiting lists of a year or more by makers of night vision gear because the U.S. military has contracts that give it priority.

"The war in Iraq escalated and the goggles weren't available," said Gary Sizemore, president of the National EMS Pilots Association and a pilot in Perry, Fla. "We were put on a waiting list."

Sizemore estimated only 25 percent of the 800 or so emergency medical helicopters in the U.S. have the technology. He said he would like such gear on his own helicopter so he could better navigate the dark pine forest he routinely flies over in northern Florida.

Night vision goggles take the tiny amount of light from the stars or the moon and amplify it hundreds of times, enabling the pilot to see in the dark and avoid flying into mountains, wires or other obstructions. The NTSB said the technology could have prevented 13 of 55 crashes of medical helicopters it analyzed in the 2006 report.

Since that study, five U.S. medical helicopters have crashed in the dark, killing 16 people, according to an NTSB database. An NTSB spokesman said it was not clear from the preliminary reports how many of the helicopters lacked night vision gear. The accidents are still under investigation and it is not known whether such equipment would have made a difference.

Just more than one-third of emergency medical flights occur at night, but they account for half of the crashes, studies show.

"Nighttime is a problem time in this industry," said David Kearns, a flight nurse in Denver. His crew uses the goggles to navigate the mountains.

The shortage came into focus last month after one of those crashes — an accident in which a helicopter used by the University of Wisconsin Hospital's Med Flight program slammed into a bluff, killing a doctor, nurse and pilot. The chopper had no night vision gear.

"There's a lot of frustration out there," said Mike Atwood, owner of Aviation Specialties Unlimited Inc. in Boise, Idaho. The company is the exclusive distributor for ITT Technologies, the nation's largest manufacturer of the latest generation of night vision goggles.

Some companies have been so discouraged by the wait that they have delayed placing orders, which only puts them further back in line, Atwood said. He said the wait time has dropped more recently to six to eight months.

ITT spokeswoman Allison Moore said the company has boosted its production capacity to try to meet demand for domestic users. Moore said the company had received orders for more than 250,000 goggles from the military since 2005.