I forget where I was flying back from, but we were just coming in to land, (at Gatwck I think)and all of a sudden the engines powered up again and we started a steep climb. The pilot came on the tannoy as calm as you like, and said that despite being cleared to land, he had seen another plane on the runway and aborted the landing to go around again. It was in the days when smokers were sat at the rear of the plane, and it was only the rear of the plane where the applause came from when we eventually landed.