American Airlines made a bid yesterday to reimpose tighter restrictions on the popular Super Saver Discount air fares but at the same time said it would afford the traveler using them larger discounts.

Effective Sept. 1, American told the Civil Aeronautics Board, it proposes to apply advance-purchase and minimum-and maximum-stay provisions on the fare's availability that are similar to those used by the airline when it introduced the Super Saver fares three-and-a-half year ago.

Under American's proposal, passengers buying the Super Savers would have to make their reservations and buy their tickets at least 30 days before departure and would have to stay at their destinations between seven and 60 days.

American said it would offer discounts of 45 percent for day flights and 55 percent for nights for domestic travel Monday through Thursday and discount of 35 percent days and 45 percent nights Friday though Sunday. The new midweek and weekend fare structure would apply to all of American's routes within the continental United States except New York-to-West Coast flights, where existing deep discounts would remain in effect.

Currently, Super Savers with discounts of 35 percent days and 45 percent nights are available to purchasers of tickets seven days in advance for trips over a Saturday night. (Some airline's discounts are 30 percent and 40 percent off.)

Robert L. Crandall, American's senior vice president for marketing, said the gradual loosening of the restrictions under competitive pressures in recent years had resulted in smaller discounts and a corresponding reduction in the number of people who could take advantage of the reduced fares. The proposal would make air transportation available to more people, he said.

An American spokesman conceded that the airlines probably wouldn't carry out the plan unless other airlines followed American's lead.

Elswhere on the fare front, the CAB formally issued its controversial interim rule granting airlines additional freedom to raise fares without the agency's involvment.

The board's decision granted airlines a three-tiered system of fare flexibility. The plan allows airlines to raise fares unlimited amount for routes of 200 miles or less, 50 percent above an agency-fixed base level for routes up to 400 miles and 30 percent above the base for routes over 400 miles. r

In response to a petition from 11 senators, who complained that the action went beyond what was envisioned by the Airline Deregulation Act and discriminated against smaller communities, the CAB asked for public comment on the fare-freedom rule by July 17.

The fare freedom remains in effect, and -- in addition to the 4 percent to 6 percent increase in fares most of the major airlines took on June 1 -- three large carriers so far have told the board they would like to increase fares another 10 percent on July 1. They are American, Barniff International and Trans World Airlines. The increases probably won't be put into effect unless other major airlines also go along.

The proposed fare increases wouldn't apply to the $88 and $99 flights between New York and the West Coast, currently the object of an air-fare war, even though officials of the major carriers, when asked, admit they are losing money with those fares. "There is no way we can make money charging $99 coast-to-coast," an American spokesman admitted.

Because the transcontinental fares don't cover the airlines' costs, some on Capitol Hill are worried that the airlines may try to make up those losses by raising fares on routes where there is little or no competition.

"That's a matter of concern to us," a CAB official said yesterday. "We're actively watching that." No one from outside the board had brought it to their attention, though, he added.

In another fare development, Pan American World Airways said yesterday it would offer new, liberalized Super Apex fares across the North and Central Pacific to replaces its "budget" fares.

The passenger would be able to book a confirmed seat as few as seven days or up to 21 days before departure, one-way or roundtrip, at fares almost half the regular economy fares. For instance, a ticket from New York to Hong Kong will cost $457 one way, compared wiht the $879 one-way economy fare.