The Kuwait Airways hijack has spawned plenty of proposals from governments, anti-terrorism experts and the public on how to tackle air piracy, but each idea invariably contains a serious pitfall.

They range from a West German lawmaker's suggestion that knockout gas be pumped into hijacked planes, to the International Air Transport Association's call for an international brigade to fight terrorism.The hijack drama, which ended in Algiers on Wednesday, left a bittersweet taste around Europe, where it unfolded daily through live TV broadcasts. The anguish and frustration it engendered was reflected in calls to radio talkshows and letters to newspapers proposing various anti-hijack strategies.

Experts noted that hijackings have fallen from 95 in 1969 to fewer than 20 a year in the 1980s. They also pointed to the difficulty the hijackers had in landing the Kuwaiti jumbo jet, saying it showed that the refusal of airports to deal with air pirates is almost universal.

But there was outrage that the nine hijackers, having killed two passengers and put others through a horrifying ordeal, apparently escaped unpunished.

Experts say the biggest problem is airport security. Some airports are extremely strict, such as in Tel Aviv where departing passengers are interrogated, while others are dangerously lax.

Paul Sheppard, security chief at the International Civil Aviation Organization, likens security to "a great spider web over the whole world, and there's no way of plugging up every single gap. The chain of security is only as strong as its weakest link."

Authorities in Bangkok, where the airliner was parked before the hijacking, say guns could have been smuggled aboard before the plane reached Thailand. But they are investigating suspicions that Thai catering staff were bribed into helping the hijackers.

"Ground staff are very poorly paid in Third World countries," says Ian Geldard of the Institute for the Study of Terrorism.

"And if people there can be bribed, hijackers are going to go for Third World countries."

One measure proposed by Geldard's London institute is to store passengers' passports in the baggage hold, thus making it difficult for hijackers to identify hostages for execution by nationality.

The Israeli newspaper Maariv reported that a California rabbi was in Tel Aviv selling a hijack survival kit containing a false passport, ID and credit card to Israelis who have good reason to conceal their identities from hijackers. Maariv said the kit costs a hefty $165.

Richard Clutterbuck, an English anti-terrorism expert, proposes issuing a fingerprinted clearance card entitling bona fide passengers to clear airports speedily, while those with no card would be searched. But Geldard says the system won't work, because states that sponsor terrorism will have little trouble obtaining the clearance cards.

West German lawmaker Johannes Gerster suggests a gas to "put the hijackers and the passengers to sleep lightning-quick." The danger, some experts say, is that if the gas failed to work instantly, it would leave the hijackers enough time to detonate explosives.

Clutterbuck says sophisticated machinery is being developed to detect explosives thermally or by neutron bombardment. But the problem, he acknowledged in an interview, is that it is expensive.

The Geneva-based International Air Transport Association, representing 168 airlines in 114 countries, proposes new international courts to try hijackers and an international commando brigade. But Geldard called this "a utopian dream," saying in an interview: "It's difficult enough to get collaboration even with firmest allies. In a lot of countries the different intelligence agencies don't even cooperate among themselves."

IATA spokesman David Kyd recalled the 1978 summit at which the seven leading industrial democracies threatened sanctions against countries that fail to bring hijackers to justice.

The threat has only once been implemented, against Afghanistan, he told British Broadcasting Corp. radio, adding: "One wonders why it hasn't been applied more often."