The Civil Aeronautics Board said yesterday it will reinstate rules requiring airlines to pay up to $400 to passengers who are "bumped" involuntarily from overbooked flights, beginning Oct. 1.

Thirteen months ago, following the firing of air traffic controllers, the CAB waived its most severe penalty for bumping, citing the disruption to airline operations.

The waived rule required an airline to pay double the one-way ticket price, up to a maximum payment of $400, if the airline could not provide alternate transportation that reached the bumped passenger's destination within two hours of the originally scheduled arrival. For international flights, four hours was allowed.

This double compensation rule was reinstated yesterday.

A less severe rule has remained in effect following the strike by the Professional Air Traffic Controllers Organization (PATCO) and was left untouched by the CAB yesterday. This provides that passengers bumped against their will must be given the face value of their one-way tickets, from a minimum of $37.50 to a maximum of $200, even if they are quickly booked on another flight.

The board had waived the double compensation provision on grounds that the airlines couldn't be expected to find passengers a substitute flight within the rule's time limits, which had been designed for normal operations.

Yesterday, the board said it was convinced that capacity is being restored to the air traffic control system and that the waiver could no longer be justified.

The agency specifically rejected the airlines' argument that the waiver should be extended because increased delays in air traffic control make them less able to predict the number of no-shows -- travelers who book reservations but don't show up for flights. The large number of expected no-shows is the reason the carriers deliberately give "confirmed" reservations to more pasengers than can be accommodated on a flight.

The agency said pointedly that the airlines could do more themselves to minimize delays but instead wanted the board to "continue to minimize the consequences" of their inaction. "This we will no longer do," it said.

The CAB rules continue to require airlines to seek volunteers who will agree to be bumped in return for a payment of the airline's choosing. Lines faced with too many passengers for a flight often offer first $50, then $100, then $150 and up, until they find enough passengers willing to step off and take a later flight.

If there are too few volunteers, however, the lines may involuntarily bump passengers according to a priority seating plan filed with the CAB and available at ticket counters.

In reinstating the normal rules, the CAB reported that the bumping rate has increased significantly.