In aerospace engineering, payload fraction is a common term used to characterize the efficiency of a particular design.
It is a function of specific impulse, propellant mass fraction and the structural coefficient.
For this reason, the useful load fraction calculates a similar number, but it is based on the combined weight of the payload and fuel together in relation to the total weight.
Propeller-driven airliners had useful load fractions on the order of 25–35%.
Modern jet airliners have considerably higher useful load fractions, on the order of 45–55%.