Airline fleets today tend to be rather large, especially the U.S. airline fleets that may have hundreds of mainline aircraft. Anyways, I was wondering how much of these aircraft are used on like a daily, weekly or monthly basis, I say that cause I dont know if airlines park certain ships on certain frequencys... during the months, weeks, or daily on the individual aircraft schedule. Basically it seems that some airlines, Delta for example, might only need no more then 30 of their 767s a day to cover their 767 route system, then again I could be wrong. I do know (as we all do) that Delta has a massive fleet of like plus 70 767s, so what My main question is, are aircraft rotated and many of the fleet not used on a daily, weekly, or monthly basis? Maybe some airlines use all there fleets on say a daily basis (maybe 90+ percent), but use each incorperated aircraft just a small amount, then it again probably depends on the airline. Well I'm extreamly interested in this subject so I'm looking forward to hearing people's advice, info etc... Thanks a lot!