EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Situational Awareness
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Security
General Flight Cancelled / Delayed
Human Factors; Procedure
Our morning began with a crew rest delay; followed by problems with ground transportation. This led to us arriving to the gate around XA:55 for our XB:05 departure. When we spoke to the gate agent she was confused; and explained they did not know about the delay. We told her about the situation and started to go down the jetbridge. At this point the gate agent informed us that 'they were all down there waiting for us.' After a few minutes of confusion it became apparent that the flight had been boarded by the agent without any crew. The gate agent thought we were on board and simply boarded 'on time without checking. In her exact words: 'I walked over; and everything looked ready. So I boarded.' The entire plane was boarded with no crew on board and unattended. The aircraft was also fueled with passengers on board and no one to perform an evacuation. I stepped on to the aircraft and immediately noticed that someone had been in the flight deck and turned the GPU power on. At this point we began to deplane the passengers. During this I contacted scheduling and dispatch to pass along what was happening. Then we performed a thorough security search of the entire aircraft.Although the only negative impact of this incident was a slightly delayed flight; this could have had a much worse outcome. This was a complete breakdown of not only safety procedures for our passengers; but also aircraft security procedures. Safety of our passengers is the most important part of what we do. It goes without saying how bad the outcome could have been had someone been in that group with malicious intent; left with a completely unattended aircraft full of passengers. Since the incident occurred before we arrived I was not personally able to find out much information. Everyone denied accessing the flight deck.
Air carrier Captain reported that the gate agent boarded passengers on the aircraft with no crew on board and unattended.