To a large extent they normally are "stored" in the air. A typical narrowbody aircraft in the US clocks 9-10 block hours a day (a little less in the air) and wi

To a large extent they normally are "stored" in the air. A typical narrowbody aircraft in the US clocks 9-10 block hours a day (a little less in the air) and widebodies even more. So somewhere around 40% of all commercial passenger aircraft are in the air at any given time (higher during the day and lower at night, of course).