VH-JIJ was being flown by a student pilot on her first solo navigation exercise. Approaching Moorabbin from the east on the last leg of the exercise, the aircraft entered controlled airspace at 4800 feet (lower level 4000 feet) without an airways clearance. The radar advisory service (RAS) controller had observed VH-JIJ on an easterly heading for some time previously at 4000 feet before climbing. When VH-JIJ entered controlled airspace at 4800 feet, VH-NCE was proceeding in the opposite direction on climb to 7000 feet and approaching the same altitude as VH-JIJ. The RAS controller gave the pilot of VH-NCE a suggested heading to avoid VH-JIJ, which at that time was unidentified traffic. The pilot of VH-NCE advised visual contact with the other aircraft as the two aircraft passed. Separation was estimated to be one to two miles laterally when both aircraft were at the same level. The pilot of VH-NCE advised that cloud in the area was scattered/broken with a base of 4000 feet. VH-JIJ was identified by transponder code as it got closer to Moorabbin. Factors The following factors were considered relevant to the development of the incident: . VH-JIJ entered controlled airspace without a clearance. . The pilot of VH-JIJ was an inexperienced student pilot.