There's actually a huge range in private planes. This M600 plane does about 7 mpg, 250 knots at 45 gph. A typical light jet might do 400 knots at 125 gph (3 mpg). But a light jet cannot not fly nonstop to a different continent. For these trips, a large business jet might do 450 knots at 300 gph (1.5 mpg), but only the very super rich can actually afford these. Even most celebrities will be flying the airlines for long international trips.