DENVER -- An order grounding much of the nation's firefighting fleet of aging, heavy-duty air tankers was lifted Saturday, two days after the second deadly crash since June in the middle of a busy wildfire season.
Still grounded pending results of federal investigations, however, were nine planes of the same types as those that crashed in June near Walker, Calif., and Thursday near Lyons, Colo., killing a total of five crew members.
A PB4Y-2 Privateer, a former Navy bomber that saw duty during World War II, came apart in the air Thursday while carrying a load of fire retardant to a blaze near the rugged Rocky Mountain National Park, about 45 miles northwest of Denver. The fire had grown to about 2,500 acres Saturday.
On Friday, the government ordered a 24-hour stand-down of 32 other tankers to allow inspections of the aircraft and to give crews a rest.
The order was lifted Saturday. Not all of the planes returned to service immediately as some contractors asked for more time to get planes ready, said Jack deGolia of the National Interagency Fire Center in Boise, Idaho.
The four-engine Privateer was built in 1945 and investigators were examining whether age was a factor.
"We haven't ruled out anything yet," said David Bowling, a National Transportation Safety Board safety specialist.
The Forest Service hires the heavy tankers from private companies that own, operate and maintain the planes, which average 42 years old. The newest plane in the fleet was built in the late 1950s, said interagency fire center spokeswoman Venetia Gempler.
The planes are subjected to high stresses because of numerous takeoffs and landings, and quick changes in weight when the cargo of retardant is dumped.
On June 17, a C-130A air tanker crashed when its wings snapped off near Walker, Calif. The five remaining C-130A firefighting aircraft have yet to return to the air.
Both crashed tankers were owned by Hawkins & Powers Aviation Inc. of Greybull, Wyo.
U.S. Forest Service records show the Privateer had logged nearly twice as many problems since 1998 as any of the other four PB4Y-2s operated by Hawkins and Powers, the Rocky Mountain News reported.
Forest Service officials contacted by The Associated Press on Saturday did not have access to the records, and Hawkins & Powers operations assistant Ryan Powers said he was not aware of excessive problems with the plane.
"Any maintenance issues that come up, we have taken care of and repaired in accordance with the standards set by the (Federal Aviation Administration)," he said.
According to the newspaper, most of the 12 problems reported on the Privateer in the past four years involved engine and other mechanical systems.
The most recent problem was in March when pilots flying to a fire in New Mexico reported an engine backfired and ran roughly, the newspaper said. The aircraft returned to service after a cylinder was replaced.
In June 1998, a pilot reported that three of the plane's engines quit simultaneously, and the plane lost 800 to 1,000 feet in altitude before the engines were restarted, the News added. Mechanics could find no explanation for the problem.
Powers said he could not recall either incident.
So far this year, wildfires have burned more than 3.5 million acres around the United States, about as much as burned in all of 2001, according to the interagency fire center.