The Reagan administration yesterday proposed legislation that would accelerate the demise of the Civil Aeronautics Board by 27 months, from the Jan. 1, 1985 date now in the law to Sept. 30, 1982.

"The domestic airline industry is now deregulated in large part," Transportation Secretary Drew Lewis said. "Early sunset of the CAB would further reduce the regulatory costs on the aviation industry, as well as eliminate the cost to the taxpayers of maintaining an agency for a longer period than necessary."

The agency is to be abolished under the Airline Deregulation Act of 1978, which set the stage for a transition of the airline industry from strict government regulation to a free, competitive marketplace.

Lewis said the administration's legislation would assume that some "needed" regulatory functions, such as the management of the subsidy program for air service to small communities and international aviation matters, would be turned over to DOT. An early dismantling by CAB Chairman Marvin S. Cohen.

The legislation proposed yesterday would:

End the CAB's special treatment of airline mergers and acquisitions and phase out authority to grant antitrust immunity in domestic aviation agreements.

Repeal certain labor laws applicable only to airline employes, leaving those matters to be covered by general labor laws.

Continue federal subsidy of essential air service to communities.

End regulation of domestic aviation rates on Sept. 30, 1982, three months earlier than the law would do now. Rate regulation is currently scheduled to lapse at the end of 1982, while the regulation of routes -- where an airline may fly within the country -- will expire at the end of 1981.

Discontinue the CAB's rate regulation on the carriage of mail. The U.S. Postal Service would get the responsibility of determining mail costs, either by competitive bidding or by direct negotiation.