The U.S. government plans to add more than 100 firefighting airplanes and helicopters to its fleet this summer to make up for 33 large air tankers that have been grounded for safety reasons, a U.S. Department of Agriculture official told Senate lawmakers yesterday.

Mark E. Rey, undersecretary for Natural Resources and Environment, said the addition of the new firefighting aircraft would make this year's fleet as effective as last year's.

As the dry summer season gets underway and Western states brace for another round of brutal wildfires, lawmakers yesterday criticized the Interior and Agriculture departments for grounding the air tankers last month. The tankers, one of the most useful tools in battling fires in the early stages, drop retardant or thousands of gallons of water from low altitudes.

"We all know what's going to happen in the next few months," said Sen. John McCain (R-Ariz.), chairman of the Senate Commerce, Science and Transportation Committee, referring to the likelihood of wildfires. "We are without a critical resource."

Three fatal accidents involving firefighting tankers, including two in 2002, led the National Transportation Safety Board to recommend major improvements in maintenance and oversight for the aircraft, which are generally more than 40 years old and subject to fatigue. In the three accidents, one or both wings of the planes detached in midair, causing the aircraft to crash.

In April, the NTSB said "it is apparent that no effective mechanism currently exists to ensure the continuing airworthiness of these firefighting aircraft." The board also found that current inspection programs "do not adequately account for the increased safety risks to which these aircraft are now exposed as a result of their advanced age and the more severe stresses of the firefighting operating environment."

Rey defended his agency's decision to ground the aircraft, made jointly with the Interior Department, by saying that a "prudent person" would not allow the tankers to continue flying without a more thorough review. Air tanker operators have been asked to submit maintenance records to the agencies, which will review them over a 30-day period, he said.

Air tankers are "a useful part of our fleet, but they are not an essential part of our fleet to maintain firefighting effectiveness," Rey said.

Mark Timmons, owner of Missoula, Mont.-based Neptune Aviation Services, which operates air tankers, said the NTSB's recommendation did not take into account extensive maintenance procedures that are already in place. "Companies do not have the luxury of hanging on for a year or year and a half" while the agencies make their safety decisions, Timmons said.