(VIENNA) - Members of the Open Skies Treaty, which allows aerial surveillance between OSCE states, launched 500 balloons Monday in Vienna to celebrate the 500th observation flight due to take place later this month, the organisation said in a statement.

Military officials from the treaty's members, which include Russia, the United States and most European states, took part in the ceremony on Heroes' Square, outside the Imperial Palace.

In total, 34 of the 56 members of the Organization for Security and Co-operation in Europe (OSCE) are party to the Open Skies Treaty, which came into force in January 2002.

"No satellite imagery can compete with an Open Skies flight when it comes to the element of openness and co-operation," Marton Krasznai, a former Hungarian Ambassador to the OSCE, said in the statement, adding it was "a useful and efficient confidence-building tool."

"There is no doubt that the treaty has made a significant contribution toward security and stability in the European area and beyond," noted US Chief Arms Control Delegate Hugh Neighbour, who chairs the Vienna-based Open Skies Consultative Commission overseeing the implementation of the treaty.

The treaty allows signatory states to conduct observation flights into other member countries to obtain military and other information.

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