Here is the Manu's post with US Navy study I was referring to (Naval Air Development Center, Guide to Aircraft In-Flight Camouflage, 1969), : it speaks about fighters, not airliners, and 10-15 miles under "moderate visibility", or 30-40 miles under "high visibility". This matches better with the day to day experience.
Cheers!
http://forum.1cpublishing.eu/showpos...1&postcount=43