B737 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 122; Flight Crew Total 2797.30; Flight Crew Type 2797.30
Situational Awareness; Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Passenger Misconduct
General None Reported / Taken
Company Policy; Human Factors; Procedure
Upon arriving at the jet for pre-flight duties in ZZZ (approximately 45 minutes prior to push) the gate agents informed us a jump seater had already been awarded and had gone down to the jet already (before passengers were boarded). This surprised us as no-one informed us and they had already let him go down to the jet (flight attendants were on-board). When we arrived on the flight deck; he was there.  He then told us it was really hot and he took it upon himself to start the APU (Auxiliary Power Unit) and put on air since it was hot in the aircraft.  My Captain was pretty upset by his actions.  He talked to him; looked through his credentials to make sure he was authorized to be a jump seater; and explained to him that that kind of behavior as a jump seater isn't good and that he shouldn't have started the APU or gone down without checking with us first. The jump seater said he was on the 737; but upon checking [credentials] it appears he was on the Airbus (for the Sep bid month anyway). The jump seater ended up getting a seat in the back.
Jump seat passenger broke protocol on B737 by entering cockpit and starting APU without flight crew on board.