This morning I was on QF108 - JFK/LAX/SYD. Coming into SYD, Air Traffic Control had delayed the slot a few minutes due to heavy traffic. After a bit of naffing around for 20 minutes or so, we were on final approach and I'm guessing somewhere around 1500-2000 feet, when the plane was put into a steep climb under full power. I was in 12J, and everyone in the cabin started to look at each other. This was the steepest climb that I can remember. After a couple of minutes the pilot announced that as a tug had broken down on the main runway and there had been one plane in front of us, he had initiated a missed approach. Not sure why a tug was on the runway. Always nice to land back in Oz after a big trip, but this was a bit too exciting.