Funnily enough, I had the same issue on a Spanair flight last week. They bused the pax to the plane before it was ready for boarding--the pax then saw one of the engineers (whom they decided was the "captain") having a look at the nose gear bay and refused to board.
It took only a couple scaremongering idiots to delay the flight for over four hours as the company finally decided to get in a replacement aircraft (and crew). Although I thought it a bit over the top at the time, top marks to the gate agent who decided he wouldn't take any shouting at his face and called in the Guardia Civil pronto--it certainly had a soothing effect on the punters
