On 12 January 2009, a Boeing 737-700 being operated by Easyjet on a non revenue function flight out of Southend and, by agreement with ATC, within a designated Military Training Area at FL150 in day VMC when there was a temporary loss of control during a planned system test. A ‘PAN’ was declared to ATC and a successful recovery was eventually achieved after an altitude loss of over 9000 ft, during which various exceedences of the AFM Flight Envelope occurred. Recovery back to Southend as originally planned was achieved without further event.