Two medical helicopter crews turned down flights — and one halted a flight — because of bad weather on the night last May when University of Wisconsin Hospital's Med Flight chopper crashed near La Crosse.

Records released Thursday by the National Transportation Safety Board do not provide a probable cause of the May 10 crash, which killed the crew of three, but the records suggest foggy conditions may have contributed.

A Mayo Medical Center crew in Eau Claire declined flights to Arcadia, La Crosse and Rochester, Minn. The crew aborted a flight to Alma Center, transporting the patient by ambulance instead.

"We turned the flight (to Arcadia) down due to the known lower clouds between Eau Claire and Arcadia," the Mayo crew said in a statement to investigators.

Allan Jacobson, a pilot for Medlink at Gundersen Lutheran Hospital in La Crosse, declined a flight to Winona, Minn.

Earlier, on the flight to Arcadia that the Mayo crew didn't take, Jacobson "noted fog beginning to form on the West side of the Mississippi River and fog and scud forming on the tops of the bluffs to his East," according to a summary of his conversation with an investigator.

Killed in the Med Flight crash were Dr. Darren Bean, 37; nurse Mark Coyne, 53; and pilot Steve Lipperer, 39. It was the first crash since Med Flight started in 1985.

The crew left Madison about 8:30 p.m. on the rainy and foggy Saturday. They picked up an 86-year-old patient in Prairie du Chien and delivered her to Gundersen Lutheran because Gundersen's helicopter was busy, officials have said. The patient died a few hours later.

The men stopped at the La Crosse airport to refuel before heading back to Madison at 10:34 p.m. At 11:04 p.m., the helicopter was reported missing. A search team found the chopper at the top of a wooded ridge about 4.5 miles southeast of the La Crosse airport about 9 a.m. the next day.

Though it was foggy that night, Lipperer "had appropriate weather minimums," said Craig Yale, a spokesman for Air Methods, a Denver-based company that leases helicopters to Med Flight.

"It was appropriate for him to fly," Yale said. "Weather is a transient thing. These things vary from flight to flight."

Toni Morrissey, a UW Hospital spokeswoman, said "we are in no position to second guess the decision of very experienced and skilled pilots and crew members."

Lipperer operated visually rather than by instruments, as is allowed under certain weather conditions, officials have said.

The helicopter that crashed didn't have two pieces of equipment recommended by the NTSB: night-vision goggles and a terrain warning system. Night-vision goggles could have helped pilots take action in 13 of the 55 medical helicopter crashes from 2002 to 2005, the NTSB said in 2006.

Terrain warning systems, which can alert pilots 25 seconds before an impact, could have helped prevent 17 of the 55 crashes, the agency said.

Air Methods has been gradually upgrading its fleet at a cost of about $100,000 each. Company officials said last year that they had to wait behind the military and other customers to purchase the equipment.

Med Flight's remaining permanent helicopter, also leased from Air Methods, is scheduled to receive the safety equipment next month, Morrissey said. That aircraft is a Eurocopter EC135, like the one that crashed.

Med Flight also has been using an aircraft on loan from Air Methods. It is also an EC135 and has the equipment, Morrissey said.

Other documents released by NTSB today said a fuel access panel may not have been properly locked on the Med Flight helicopter that crashed. Yale said it's highly unlikely that was a factor in the incident.

Lipperer had no drugs in his body, and the chopper's engine was operating normally, other documents said.

An NTSB analysis of the incident, including a probable cause, will be released later, said Keith Holloway, a spokesman for the agency.

The NTSB released the Med Flight crash records along with reports for eight other fatal medical helicopter crashes from December 2007 to October 2008. The nine crashes killed 35 people.

When the NTSB last closely analyzed the safety of medical helicopters in 2006, 55 crashes had killed 54 people from 2002 to 2005. Crashes were down in 2006 and 2007.

The recent string of fatalities has led the agency to organize a four-day public hearing on the issue next month in Washington, D.C.

"We have seen an alarming rise in the numbers of EMS accidents," Robert Sumwalt, a member of the board, said in a news release announcing the public hearing.

UW Hospital has been discussing a memorial or tribute to the Med Flight crew, but no details are available, Morrissey said.

The dates and locations of the other crashes for which reports were released today: Dec. 3, 2007, Whittier, Alaska; Dec. 30, 2007, Cherokee, Ala.; Feb. 5, 2008, South Padre Island, Texas; June 8, 2008, Huntsville, Texas; June 29, 2008, Flagstaff, Ariz.; Aug. 31, 2008, Greensburg, Indiana; Sept. 27, 2008, District Heights, Md.; Oct. 15, 2008, Aurora, Ill.