Open Skies Treaty
The Open Skies Treaty is part of the OSCE's arms control system.
The 34 signatories conduct unarmed aerial surveillance and photography in each others' air spaces. The aerial surveillance flights help member states to keep up-to-date on each others' military developments.
Finland signed the agreement in 2003 and is obliged to host five Open Skies flights a year.
All data gathered during these flights is freely available to all signatory countries.