The U.S. Court of Appeals for the District of Columbia yesterday struck down a ban on political advertising in display cases at National and Dulles airports.

Citing the First Amendment's guarantee of freedom of speech, the three-judge court reversed a 1981 decision by the U.S. District Court that said the Federal Aviation Administration (FAA), which operates the two airports, could bar political advertising in display cases. The court also sent the case, filed by the registered agent of the Namibian government that had sought to place political advertisements in the airports' display cases, back to the lower court.

"Many people pass through these airport terminals with the hopes of soon witnessing the workings of the national capital and the symbols of this nation's principles," wrote Judge Abner Mikva for the court. "It is only fitting that these people are presented with tangible proof that the first amendment is operative and not simply on display in a glass case at the National Archives."

David Hess, a spokesman for the FAA, declined comment until government lawyers had studied the decision.

"It's a very important decision," said Thomas Henry, a lawyer for the appellant, which represents the Namibian government in the United States. Henry said the decision opens the way for political advertising of all sorts, including campaigning by U.S. political parties, at the two airports.

The proposed advertisements were to be placed in display cases in corridors at National Airport and in baggage claim areas at Dulles. More than 16 million passengers pass through the two airports each year, Hess said.

The suit was brought by the U.S. Southwest Africa/Namibia Trade & Cultural Council, a registered foreign agent representing the government of Namibia (Southwest Africa), a colony of South Africa, which holds the territory under a United Nations mandate.

The display advertisements that the council sought to place in the airports criticized the Southwest African People's Organization (SWAPO), a black nationalist guerrilla movement fighting to wrest control of Namibia from South Africa and its allies in the territory.

The proposed advertisements were entitled "SWAPO's Rape of Namibia," and accused the guerrilla group of being a "Soviet-bloc terrorist group."

In November 1980, the council sought to place the ads at the airports, but the FAA, citing a longstanding ban on political advertising at the airports, denied the request a month later. The council appealed unsuccessfully to the U.S. District Court, and yesterday's decision overturns that court's finding.

"We are aware that our society's commitment to robust--even irritating--debate at such public forums will not be easy," the court said. "But the creation of such disquietude is the very purpose of the amendment placed in our Bill of Rights."

Henry, the council's lawyer, said the airports are "a tremendous medium" for advertising. "You have nothing else to do but read the ads when you're walking down the halls," he said.