Correctly sizing small feeder aircraft is a process based on lane requirements (amount of outbound/inbound cargo volume) average package density (lbs/cu ft), aircraft pricing and reliability.  Alpine determined that average stage lengths are less than 500 miles and typical package density is between 5.5 – 6.0 lbs/cu ft.  Inefficient aircraft planning can result in aircraft that fill their cubic capacity before they fill their weight capacity.  Flight planners can exchange shorter range for increased useful load, but most efficient flights occur when cubic capacity is achieved at the same time that max carry weight occurs.  We have determined that equilibrium occurs using the Beech 99, the Alpine Super Freighter 1900D and the EMB120.  Volume requirements less than 450 cu ft is most efficiently carried in a 99. The 1900D can carry up to 900 cu ft and an EBM120 can carry up to 1185 cu ft.  The most cost-efficient aircraft up to 700-900 cu ft is, without question, the 1900D.