A soldier in the Philippines stands guard against terrorists

Hoping to prevent a repeat of last month's attacks in the United States, members of the International Civil Aviation Organisation (ICAO) recommended that cockpit doors be locked during flights and that international security standards are enforced on domestic flights.

The United States is already tightening aviation security with more thorough passenger screening at airports and the use of sky marshals - armed, plain-clothes guards who travel on domestic flights.

The important thing is to take preventive measures at the airports

ICAO president Assad Kotaite

But ICAO president Assad Kotaite said tighter screening of passengers was the key to preventing hijacks.

"The important thing is to take preventive measures at the airports.

"This is really the essential, rather to have them at the plane and to have air marshals and start to fight on the plane."

The decision to help meet the cost of this programme is a vital one for ICAO.

Many of the poorer countries represented in Montreal said that they would find it difficult to pay for increased security measures or to check whether private companies were following them.

New threat

The extra funds will help every country to reach and maintain a higher standard of security.

The safety and security panels of ICAO are also to review all current regulations in time for a special ministerial conference on aviation safety which they hope to hold in Montreal before the end of the year.

Speakers at the conference stressed the need for better security, describing the 11 September attacks as the first in which planes were used as a weapon of destruction.

This, they said, posed a significant new threat to civil aviation.

The ICAO was created by the United Nations in 1944 to set international standards and regulations for safety and security of civil air transport. It has a $57m annual budget.