An Alexandria federal judge fined an Arlington export firm $10,000 yesterday for aiding and abetting the illegal transport of munitions to Chile between l979 and l981.

American Aviation Parts and Service Corp. pleaded guilty to selling $48,000 worth of restricted equipment, including jet fighter parts, to the Chilean Air Force Mission. The parts were destined for Santiago. Federal law has prohibited the sale of munitions to Chile without a special license from the State Department since 1976.

As part of the Oct. 26 plea bargain agreement, Assistant U.S. Attorney Lawrence J. Leiser agreed not to prosecute the company for selling additional equipment valued at $130,000 during the past two years.

Leiser said diplomatic immunity exempted any members of the Chilean Air Force Mission from prosecution.

American Aviation, a firm owned by Sunder Kundanmal at 1735 Jefferson Davis Highway, purchases equipment and services from American manufacturers and sells them to foreign governments. The vice president of the company, Elizabeth Mutter, said in a court affidavit that the company transported all the munitions sold to the Chilean Air Force Mission to the International Export Packers shipping firm in Alexandria for ultimate shipment to Chile.

In the last two years, four different Northern Virginia companies have been prosecuted for sending restricted munitions to foreign governments, Leiser said. Prior to that, he said, he did not recall any such cases.

The maximum penalty for aiding and abetting the illegal transport of munitions is two years in prison and a fine of $100,000.

U.S. District Judge Albert V. Bryan Jr. ruled that if American Aviation sold any further illegal supplies to Chile, its officers, directors and employes could face criminal prosecution.

Among the items sold were missile launch brackets, periscopes, target towing adapters and several F-5 fighter plane parts.