Airline discount certificates from a massive price-fixing lawsuit started going in the mail Thursday, a federal court master announced.

The certificates will be mailed up to Dec. 31, said Dawn R. Smith, special administrative master for the U.S. District Court. Many of the people with claims may not receive their certificates until sometime in January because of the crush of holiday mail, she said.A settlement was approved by U.S District Judge Marvin H. Shoob in 1993, but it took more than a year to finish processing the 4.3 million claims.

Certificates are being written in amounts of $73 for claims of fewer than five round trips, $75 for claims of at least five round trips and $79 or more for claims exceeding $2,500 in value, Smith said.

The largest claimant, IBM, will receive about $3.3 million in certificates.

Recipients can use the coupons immediately to buy tickets, though they cannot be used for travel on the first three days of the year, which are blacked out along with periods around Thanksgiving and Christmas.

Filed in 1990, the lawsuit alleged airlines used a computerized reservations system to mutually raise ticket prices. The airlines denied wrongdoing, but last year agreed to a $458 million settlement that covers discount coupons, court costs and attorney fees.

The Atlanta case was one of three suits brought in recent years alleging price-fixing. All were settled without a trial. Named in the lawsuit were American Airlines, Northwest Airlines, Pan American World Airways, Delta Air Lines, Midway Airlines, Trans World Airlines, United Airlines, USAir and Continental Airlines.