Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 75; Flight Crew Total 7000; Flight Crew Type 1500
Communication Breakdown; Fatigue; Human-Machine Interface
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance
Human Factors; Procedure
Entering the terminal area after an overnight oceanic flight from the United States. The flight planned route terminated with a STAR. Based upon our experience from previous trips; we were expecting the RNAV Transition following the STAR to end up with an ILS to runway 26R. During the STAR; Approach cleared us to ZZZZZ and ZZZZZ1. We were NOT cleared for the RNAV Transition. We entered the waypoints and continued.  We were then handed over to the Final Controller. Passing ZZZZZ1 we were told to expect the ILS Runway 26L approach (we previously were expecting the ILS 26R). At that point the PIC (Pilot Not Flying) was focused on changing the approach in the FMS. As the aircraft passed ZZZZZ1; the aircraft began a right turn based on the ILS being loaded into the FMS. We immediately asked the Controller for a heading and were given a turn back to 070. We then took vectors for an ILS 26L and completed an uneventful landing. At no time did we come near any other aircraft (noted both visually and on TCAS).The RNAV Transition notes that at ZZZZZ1 the aircraft should maintain track and expect radar vectors to the final approach.In our minds; this event developed due to a combination of a bad clearance from Approach and our failure to confirm what actions would be required following ZZZZZ1. If Approach had cleared us for the entire RNAV Transition; the procedure loaded in the FMS would have prevented us from turning towards the runway at ZZZZZ1. Further complicating the issue; upon initial contact with the Final Controller; aircraft are expected to state only their call sign; again; a full check in might have increased situational awareness for both our crew and ATC. Given the long oceanic flight and our operations within a circadian low; we believe that fatigue was a factor in this event. We intend to share our experience with our entire pilot group to ensure that as a team we learn from this situation.
A corporate flight crew on an international arrival started a turn to the initial approach fix before asking for further clearance.