>Whats the max permissable drift allowed on the 767 Ian? I can't recall if the following chart was for the 767 or the 747-400, but they should be pretty much the same, Stuhttp://www.ozemail.com.au/~iriddell/Error.gifAs you can see, the allowance is quite large (almost up to 35nm on a single trip of 10 hours duration).>An other point on GPS, i was reading in New Scientist that >its very easily Jammed by a simple made transmitter. so much >so its causeing some concern to the UK and US Defence >departments.A fellow New Scientist reader eh? :-)Cheers.Ian.

Hi IanYup, its a good read, the bit about GPS is 28th sept eddition.page 20, just a tiny column on it.Cheers Stu.