I don't really want to stir bad blood as there are many twists and turns, but the pilots had Hawkes support on a particular issue when he was president of the ACTU. Sometime later he asked for their support in boycotting certain refueling locations in a separate industrial dispute which he assumed he had in the bag. It didn't go as planned and for one reason or another the pilots did not support the initiative and it all fell in a heap for Hawke. From that moment on he took it personally and went after the whole lot at the first opportunity which was handed to him on a silver platter when in office and '89 began to unfold.
Perhaps a few others can fill in the smaller details.