I googled and found that someone had already calculated an answer for this question. I would have thought that a true answer will depend on wind conditions.
I cant see the exact reference I found last night but this one has a few answers
http://answers.yahoo....20080702142825AAZecpZ
Thanks for the answer grasscarp,I just wandered if you were in the aviation industry. I was under the impression that Jet aircraft were very poor "Gliders" nice to know they are better then i thought
I am in the aviation industry, for the past 20 years plus in the flight planning area. I also hold a commercial pilots licence. This link gives a lot of information and links and quickly reading down it, also says from 30,000 ft - 75 nautical miles, so very close to what I already gave.
http://www.airliners....on/read.main/2499076/