Phase One of a proposal by the UK Civil Aviation Authority (CAA) to improve airspace capacity will require aircraft owners in the UK to upgrade to a Secondary Surveillance Radar (SSR) Mode-S transponder by March 31, 2012. In addition, all new installations of SSR transponders must be Mode-S compliant beyond March 31 next year. Phase Two will require all VFR flights within controlled airspace to be equipped with SSR Mode-S by March 2009; establish transponder mandatory zones within certain areas of uncontrolled airspace; and require all international flights to operate with Mode-S. Phase One of the proposal was announced in response to last year’s public consultations and meetings with representatives of GA associations, National Air Traffic Services and the Ministry of Defence. Phase One will be submitted to the government later this year, and a public consultation for Phase Two is also tentatively scheduled for that time frame.