The nation's oldest and noisiest jetliners would go into retirement a decade early under the government's new aviation noise-reduction plan, the Transportation Department's No. 2 official says.

Deputy Secretary Elaine L. Chao said the proposed regulation is balanced, permitting expansion of commercial air service while helping communities seeking relief from earsplitting noise near airports.Speaking at a public hearing on the proposal, Chao called the plan to phase out noisy "Stage 2" aircraft by the end of the century and replace them with quieter planes "strong and sensible" despite its estimated $4.4 billion price tag.

But a spokesman for the airline industry said more flexibility is needed to help weaker airlines make the adjustment. Representatives of noise-reduction groups expressed disappointment, saying they want swifter and more decisive action.

Annette Davis, representing Citizens for the Abatement of Aircraft Noise, called the proposal "hasty and ill-considered."

She said it will effectively bar local groups from exerting pressure to ease local noise problems. Davis called for a phaseout of Stage 2 planes at nearby Washington National Airport no later than the end of 1993.

Until that happens, she said, "there is nowhere to hide from the brutal effect of noise on our lives."

At a separate appearance Tuesday before the House Public Works and Transportation Committee, Alfred A. Checchi, co-chairman of Northwest Airlines, said the proposed regulation, required under a 1990 law, said the whole idea is flawed and should be reconsidered.

"Only about one percent of Americans live within the noise `envelope' and virtually all of them bought homes adjacent to pre-existing airports," Checchi said. "For the benefit of these few people, the industry will incur billions of dollars in costs."

The proposed regulation will require Northwest and other airlines to retire large numbers of aircraft "well before the end of their useful lives," Checchi said.

As Stage 2 airplanes are replaced by quieter but more expensive Stage 3 planes, the biggest loser will be small communities, he said.

"Air service to these communities, which is currently marginally profitable with $5 million aircraft, will become impossible with $30 million replacements," he said.

As proposed by the Transportation Department and the Federal Aviation Administration, the fleet of old and noisy Stage 2 planes would be reduced by 25 percent by the end of 1994, 50 percent by the end of 1996 and 75 percent by the end of 1998.

All such aircraft would have to be eliminated, or modified to meet noise-reduction standards, by the end of the year 2000.