All 5 aircraft in the Airbus A350-900 test fleet have taken part in a formation flight, ahead of certification of the type.
Using the callsign ‘Carbon’, the aircraft departed Toulouse’s runway 14R at about 10:30, led by the first cabin-fitted airframe MSN2.
The formation subsequently joined up and performed several east-west flights parallel to the Pyrenees mountain range.
http://www.airliners.net/photo/Airbus/Airbus-A350-941/2510572/L/
Based on the article "A350s fly in formation ahead of certification" published in FlightGlobal.