Major airlines cannot be forced to obey a civil rights law that prohibits discrimination against the handicapped, the Supreme Court ruled yesterday, because they do not receive direct federal assistance.

In a 6-to-3 ruling, the court said that while airlines benefit from using federally funded airports and the federally run air traffic control system, such indirect aid does not bring them under the coverage of the Rehabilitation Act of 1973. A handful of small airlines that receive mail subsidies are subject to the 1973 act, under yesterday's ruling.

The decision, written by Justice Lewis F. Powell Jr., reaffirmed the court's controversial 1984 ruling in Grove City College v. Bell, in which the justices limited the scope of four major civil rights laws to those "programs or activities" that receive federal aid.

Civil rights groups have attempted to overturn that ruling but have been stymied by fights over antiabortion amendments.

In the airline case, Department of Transportation v. Paralyzed Veterans of America, handicapped groups argued that airlines were covered by the antidiscrimination law because they benefit from federal funds given to airports and from the federally run air traffic control system.

The Reagan administration, which has fought successfully for a narrow interpretation of civil rights laws, disagreed, saying that airlines were not required to accommodate the special needs of the handicapped. The administration argued that a federal appeals court ruling here had improperly extended the scope of the 1973 law and misinterpreted the Grove City decision.

Powell agreed, saying that Congress intended the 1973 act to cover only the actual recipients of federal aid, and not indirect beneficiaries. To rule otherwise, he said, "would give the 1973 law almost limitless coverage."

"By limiting coverage to recipients," Powell said, "Congress imposes the obligations of the law upon those who are in a position to accept or reject those obligations as a part of the decision whether or not to 'receive' federal funds. In this case, the only people in that position are the airport operators," not the airlines.

Justice Thurgood Marshall, in dissent with Justices William J. Brennan Jr. and Harry A. Blackmun, said, "Commercial airlines are in a unique position to deny public access to federally funded airport and airway services."

"Commercial airlines thus necessarily act as gatekeepers," he said, "controlling who shall enjoy . . . important benefits under federally funded . . . programs."

James E. Landry, general counsel for the Air Transport Association of America, said, "We're gratified by this decision on an important legal question. But it should be appreciated that regardless of the ruling, the airline industry will continue to meet the needs of all its passengers, including particularly its handicapped passengers."

Arlene Battis, an attorney with Paralyzed Veterans of America, said handicapped groups would now seek congressional legislation to stop airlines from discriminating and to make sure the handicapped traveler is able to travel.

In another case yesterday, the court ruled that religious schools may be required to obey state laws banning sex discrimination, but said federal courts should not step in until state administrative agencies had completed their enforcement actions.

Justice William H. Rehnquist, writing for the court in Ohio Civil Rights Commission v. Dayton Christian Schools, overturned a 6th U.S. Circuit Court of Appeals ruling last year that barred Ohio officials from investigating a charge of sex discrimination at a religious school.

The appeals court said the First Amendment's protection of freedom of religion prohibited the state civil rights commission from enforcing Ohio's law against sex discrimination in the case, which involved a teacher who was suspended from her job after having a baby. The school said its religiously based philosophy was that mothers of preschoolers should stay at home. School officials, citing a pledge she had made not to take school officials to court, fired her after she sought the advice of a lawyer.

"Even religious schools cannot claim to be wholly free from some state regulation," Rehnquist said. The school's constitutional claims could be considered after the state decided what action, if any, to take, he added.

"We have no doubt that the elimination of prohibited sex discrimination is a sufficiently important state interest," Rehnquist said, adding that the court also had "no reason to doubt that the school would receive an adequate opportunity to raise its constitutional claims" to state officials.

"The commission violates no constitutional rights," Rehnquist said, "by merely investigating the circumstances of the woman's firing in this case, if only to ascertain whether the ascribed religious-based reason was in fact the reason for the discharge."