The crew of the Airbus Industrie A340 responded to a traffic alert and collision avoidance system (TCAS) resolution advisory (RA) and climbed 600 ft above the cleared level of flight level (FL)190. The conflicting traffic was a formation of military McDonnell Douglas Corporation FA-18A Hornet aircraft in transit through a military airspace corridor. Traffic information was passed to the crew of the A340 by the air traffic controller. The Hornet crews were on military control frequencies. At the time of the TCAS alert, the Hornets had climbed to FL180 from FL170 to transit civil airspace via a military airspace corridor 75km north of Sydney, known as the Hunter Corridor. Civil radar data indicated that the Hornets climbed to FL183 and military radar data indicated a climb to FL182. The crews stated that they were positive that they had levelled at FL180, and that they had the A340 in sight. Analysis of the radar data indicated that, at the time of the resolution advisory, the standard vertical separation had reduced to less than 1000ft resulting in an infringement of separation standards.