IT'S BRACING THAT the seven industrial nations meeting at Bonn, who dominate international air traffic, decided to suspend air service to and from any country that harbors hijackers. Neither Japan nor Canada, who promoted the idea, nor the United States has air links with the haven countries: Libya, South Yemen, Iraq and sometimes Algeria. International terrorist hijackings have fallen from the 1970 high of 21 to a recent average in the 3-4-5 range. The decline can be attributed to better security, the enlistment of conservative Arabs to fight hijacking after some of their own officials were victimized, and a realization by some Palestinians that hijacking hurt their cause. Still, the Bonn seven have set a good example of solidarity. If France and Italy, who have air links with haven countries are serious, the skies will be a safer place.

The Bonn declaration is useful for another reason. It draws attention to the United States' own efforts to fight international terrorism. The American pledge at Bonn actually is weaker than the authority given the president in legislation in 1974 to suspend air traffic not only with havens but also with countries aiding hijack organizations. No part of that well-meaning legislation seems ever to have been invoked. That is a basic reason why more sharply focused legislation, sponsored chiefly by Abraham Ribicoff (D-Conn.), has been moving through the Senate. It's about a month away from virtually certain floor passage, and a parallel House measure is not far behind.

The Ribicoff bill would set up a procedure to warn American travelers about foreign airports that don't meet American anti-hijacking standards. Beyond that, it would provide for broad economic sanctions against countries that "demonstrate state support" - training, arms, false passports, funds, sanctuary, etc. - for acts of terrorism of any kind (not just skyjacking). The White House happened to focus on the bill just as the president was starting to worry about congressional restrictions on foreign policy, and that has produced an argumeent over whether the president should be able to impose sanctions at his own discretion or whether he should have only the power to waive sanctions imposed by Congress. But otherwise the administration supports the Ribicoff bill.

Terrorism in the form of skyjacking may not be the menace it once was, but terrorism in other forms will be a menace indefinitely. No single declaration or law can construct the deterrent and defense that the international system requires for its safety and psychological ease. But all of these efforts can help build the bulwark that all nations need.