Open Skies Treaty between Hungary and Romania
The Open Skies Treaty between Hungary and Romania was a bilateral agreement between Hungary and Romania in force from 1992 to 2001. The Treaty became effective on 27 February 1992 and consisted of agreed-upon surveillance overflights between the two countries to assess the strength and disposition of opposing military forces.
Source: Wikipedia — Open Skies Treaty between Hungary and Romania (CC BY-SA 4.0)