TUCSON, Ariz. — Two fatal helicopter crashes at the Grand Canyon have spurred the National Transportation Safety Board to issue safety recommendations to air tour operators and to the Federal Aviation Administration.

In a letter issued Wednesday, the NTSB recommended that the Tour Operators Program of Safety — a domestic organization for the air tour industry — expand its safety audit program to include a review of records of all safety-related complaints and correspondence about pilot performance.

It also said that program should be increased to include en route surveillance of all commercial air tour routes flown repetitively around the Grand Canyon and that its guidance materials be revised.

A call to the head of TOPS seeking comment was not returned immediately Thursday.

But Steve Bassett, president of the United States Air Tour Association, called the NTSB's portrayal of the safety of the Grand Canyon air tour industry "unfair, unjustified and misleading."

He said the agency's singling out and targeting the commercial air tour industry nationwide "is neither justified nor deserved."

The companies singled out were "exemplary Grand Canyon operators and pioneers" and "deserve far better treatment" based on their overall safety records and dedication to flight safety, Bassett's statement said. "The timing and substance of these recommendations is troubling at best."

"We have 90 days to respond to the NTSB recommendations, and obviously will do so," said Ian Gregor, an FAA spokesman in Los Angeles. "Generally, air tour safety is something that we've paid an awful lot of attention to over the years."

An FAA rule implemented in 1987 for air tour flights at the Grand Canyon and still in effect was aimed at reducing the risk of midair crashes, reducing the risk of accidents from pilots flying below the rim level and at reducing aircraft noise impacts, Gregor said.

Among other things, it established minimum flight altitudes for various parts of the canyon, established areas in which people were prohibited from flying and also limited how far certain air tour operators can fly from their bases, he added.

The NTSB letter cited unsafe pilot flying procedures and misjudgment as the probable cause of both the September 2003 crash of a helicopter operated by Sundance Helicopters Inc. that killed its pilot and six passengers and that of a chopper operated by Papillon Airways Inc. in August 2001 in which five passengers and the pilot died.