UA839 SYD-MEL (6/5/12)

[Jayden Laing]

Question for the engineers/pilots on the B744's:

Today I noticed UA839 (SYD-MEL) taxying to 16L via Golf & Charlie. When I saw it crossing 34L on taxiway Golf I noticed that the number 3 engine had not been started and engines 1, 2 & 4 were all running. NOW my question is, when UA839 departed, IS/WAS it possible that it only took off with 3 engines operating at the time of departure or did the crew start the number 3 engine whilst holding short of 16L? If it did depart with only 3 engines operating, would there be signifcantly more stress on the airframe/wings rather than if all 4 engines were operating?

This just caught my attention as it was the first time I had seen this & I wanted to pose the question out there to see what anyone has to say.