Last month, Eastern Airlines distributed more than 200,000 "California Bonus Coupons" on its Air-Shuttle. Each coupon entitles the bearer to a 50 percent discount on a one-way Eastern flight between New York and California through June 10.

No sooner had Eastern begun distributing the coupons than the other major transcontinental airlines said they would redeem Eastern's coupons for their own flights, not only from New York in most cases but also from Washington, Baltimore and Boston and to San Diego in addition to Los Angeles and San Francisco.

This week, citing new jet-fuel price increases and low passenger traffic, Eastern announced that it was pulling back its cross-country service, leaving one round trip a day between New York and Los Angeles, down from three, and one round trip, between New York and San Francisco, down from two a day.

The other airlines remain with a full schedule -- and committed to honor Eastern's half-fare coupons on their own flights. Are they angry? It doesn't appear so. Eastern seems to have caused the airlines a lot more distress last June when it began its cross-country service with low fares.

"It's been our feeling all along that there has been excessive capacity in this market, especially with traffic declining," American Airlines' spokesman Al Becker said yesterday. "We find it an encouraging sign that they have reduced their participation."

Becker's comments were seconded by officials of United Airlines, Trans World Airlines and Pan American World Airways. "The name of the game these days if to fill seats," a spokesman for Pan Am said. "Eastern's pulling out means that we'll have a greater percentage of seats filled."

He noted, however, that Pan Am's cross-country flights from New York may have a greater percentage of seats filled because they go on from the West Coast to the Far East.

Spokesman for the airlines said generally that few coupons have been redeemed so far, despite the vigorous buy-and-sell market for the coupons as passengers got off shuttle flights with them.

As for Eastern, its officials say it has an obligation to honor the coupons and intends to make sure all passengers are accomodated despite the reduced schedule. "We'll take care of them," an Eastern spokesman said.

Eastern plans to boost its service again in June, he said.