The crash this week of the Pan Am 747 that took nearly 300 lives appears to security and aviation authorities to have all the earmarks of a terrorist bombing attack.

Consequently, this sad episode should focus the world's attention on how much it has yet to do in combatting terrorism.Terrorism has been in the news again, as both bad and good news, with the destruction of the jet and the announcement by PLO leader Yasser Arafat that his group has renounced its use.

While Arafat's statement is welcome, the 747's destruction shows terrorism is still considered a valid weapon by fringe hate groups and the nations that harbor and support them.

Civilized nations have called for sanctions against countries such as Iran, Libya, and Algeria that are known to support terrorists. Unfortunately, too many of the countries have paid only lip service to the sanctions, continuing to maintain "business as usual" relations with the outlaw countries.

More pressure should be applied. President Reagan's statement early in his administration that terrorists can run, but not hide forever, should be the guiding philosophy in a worldwide coordinated effort to stamp out terrorist groups and make the price of supporting them too high.

Arafat's PLO has denied any connection with the 747's destruction. Some fringe groups, however, have stepped up to claim responsibility.

If Arafat is serious in his renunciation and serious about opening dialogue and relations with the West, he could go a step further to prove he is in earnest: Tell security and intelligence agencies what he knows about active terrorist groups as a first step to rooting them out. But don't hold your breath waiting for that to happen.

Meanwhile, authorities should brace themselves for the chilling possibility that the hate-crazed anti-Americans who blew up the Pan Am 747 this week may commit such atrocities again and again.