Six years after Congress directed the Pentagon to cull its fleet for aircraft that could be converted to firefighting tankers, the first replacement has yet to arrive.

"It's time for the Defense Department to act," said Sen. Jeff Bingaman, D-N.M., who wrote the law authorizing the Pentagon to sell excess planes to companies that fly firefighting missions for the Forest Service.

Thirty-two firefighting air tankers with manufacturing dates on file with the Federal Aviation Administration have an average age of 47 years. The oldest rolled off the assembly line in 1943, while the newest is 36 years old, according to FAA data.

"We badly need to replace some old stuff," said Ed Stone, branch chief of aviation policy for the U.S. Forest Service.

Debra Bennett, a Pentagon supply systems analyst, said the military doesn't have any excess aircraft now and hasn't since 1996, when Congress directed that they be offered for sale to firefighting companies.

Only after each branch of the military -- Army, Navy, Air Force, Marine Corps, National Guard and Reserve units -- rejects the chance to claim a plane does it move to the excess category, Bennett said.

"It is a rare occurrence that an aircraft gets to that point," she added.

In contrast with "surplus" planes that no longer have any value to the military and can be sold publicly, excess planes are classified as still having some military value.

The Forest Service owns no planes. It says it's cheaper to contract with private companies, which then are responsible for maintaining and flying the planes. This year the service is using 45 planes from 10 contractors.

The severity of fires this year has forced the tankers to fly more than double their usual number of hours. Through July 24, the tankers had logged 7,658 hours in the air. In most years, they fly 5,933 hours all year and average 3,451 hours through July 25.

Three people were killed in June when the wings separated from a C-130A being used to fight a fire in California. Two weeks ago, a PB4Y-2 broke up and crashed while fighting a Colorado blaze, killing its two-man crew.

The planes were 46 and 57 years old, respectively. Investigations into those crashes are ongoing and it is unclear if age played a role.

"The type of flying we do is harder on an airplane than going from New York to San Francisco," said Bob Wofford, a pilot and trainer for Neptune Aviation out of Missoula, Mont., and chairman of the Associated Airtanker Pilots. "If we're going to have a viable airtanker fleet in the future then the government is going to have to step in and provide some help."

Forest Service officials, contractors and pilots all say the issue with old planes is not one of safety. With proper maintenance, old planes can be flown safely.

But newer aircraft can drop more retardant, cost less to maintain and service, and don't use the leaded aviation fuel that is becoming scarce, said Bill Broadwell of the Aerial Firefighting Industry Association.

Contractors say buying used military aircraft is the only way they can afford to upgrade their fleets. Agriculture Secretary Ann Veneman earlier this year sent Defense Secretary Donald Rumsfeld a list of planes of interest to Forest Service contractors. They include a Navy submarine hunter called the P-3A and two models of a military transport called the C-130B and C-130E. The C-130B has been in production since 1959 but is still seen as a step up.

A Forest Service task force six years ago set a goal of replacing all the existing tankers with 41 military planes by 2016. Its timetable called for the first 11 of those aircraft being in operation this year.

However, the Defense Department took four years to write rules for the sales. By the time the rules were done, the initial congressional authorization had nearly lapsed. Congress then extended the act to 2005 and the Defense Department said it needed to rewrite the rules, even though the wording remained the same. That process is ongoing.

In May, 23 House members wrote Rumsfeld, urging him to expedite the sales. They have not received a response.

"I'm not very optimistic that it's ever going to happen," said Hank Moore, co-owner of TBM Inc., which does aerial firefighting for the Forest Service.