DALLAS - Changes are circling for the emergency medical helicopter industry, which saw a disturbing number of fatal crashes last year.

Twenty-nine deaths in 2008, compared with seven in 2007, spurred calls for regulators to impose new rules for helicopter operators. But some feel that has not been enough; Congress is now poised to pass a series of rules governing the nation's fleet of medical helicopters.

Three recent crashes of medical helicopters have reinforced concerns that the flights often put pilots, medical crew, and injured patients in danger.

On Sept. 25, a medical helicopter owned by Omniflight Helicopter Inc. crashed in South Carolina, killing three people; on Nov. 4, two pilots of an Omniflight training flight were injured in a crash in Arizona; and three people died in a Nov. 14 medical helicopter crash near the border of Nevada and California.

"We've had many pilots with many years of experience who have gotten into these accidents, and we need to know why," said Gary Sizemore of the National EMS Pilots union. "Our pilots are facing a lot of pressures."

In the South Carolina accident, the helicopter crashed in a tree farm near the Charleston airport during heavy rain. The investigation continues, though weather played a role, National Transportation Safety Board staff members say.

Getting medical helicopters through bad weather, especially at night, may help curb the conditions that lead to a majority of accidents, regulators say.

In September, the NTSB urged the industry's regulator, the Federal Aviation Administration, to require night-vision gear, terrain avoidance equipment, and cockpit data and voice recording devices for helicopter operators. The NTSB put the recommendations on its "most wanted" list and urged helicopter operators to install the safety equipment on their own.

"You'd think our recommendations would get more traction," said Keith Holloway of the NTSB. "I can't tell you why they're not acted on."

FAA spokesman Les Dorr said the agency uses a variety of enforcement tools to make medical helicopter operators safer, such as requiring training programs related to operators' licensing certificates. The agency said it has also recommended that operators add risk-assessment programs and operational control centers.

Dorr said the FAA expects to publish new safety rules related to the segment by the middle of next year.

Congress could force the issue with the FAA. Language in a bill pending in the Senate would force the regulator to start a rule-making procedure that would eventually require new on-board equipment, better ground-based weather detecting and improved safety programs.

The House has already passed a version of the bill, which would also force the FAA to order studies on whether to require night-vision equipment in helicopters as well as improved weather detecting systems.

The legislation, which would reauthorize the FAA's funding, could be passed before the end of the year.

Emergency medical helicopter operators welcome more regulation, said Christopher Eastlee of the Air Medical Operators Association.

His group has praised the language in the House bill. "We're trying to identify inefficiencies in this system" by working with regulators, he said. Adding gear to helicopters would cost tens of thousands of dollars and put financial pressures on operators, but most are already spending money on night-vision systems and equipment that records flight data, he said.

Omniflight said will add flight data recording to all its aircraft. The company previously announced that it was putting night-vision systems on some of its fleet.

The 1,000-employee company, bought by a private equity firm in 2005, declined to comment on how new regulations might affect its business.

Emergency operators are a hodgepodge of public and private hospitals, independent companies like Omniflight and publicly traded companies. Operators typically collect payment from patients' insurers or from Medicare.

Omniflight, which has grown quickly to have a fleet of 100 helicopters spread over 18 states, is a prime example of how the industry has taken off over the last two decades, rising from 225 aircraft in 1991 to more than 850 today.

Some point to a 2002 increase in the Medicare reimbursement rate as the start of industry's fast growth. The change allowed operators to recoup substantially more of their costs to fly missions, which can cost $10,000 or more, depending on the emergency.

According to the NTSB, the need for emergency flights has increased to where 400,000 patients and transplant organs are transported annually. That compares with about 150,000 patients flown in 1991, according to the air operators association, though that number does not include flights transporting organs.