In the concept of aerodynamic tunneling,an object is transported from terrestrial point A to B via a closed tube containing an atmosphere more aerodynamically favorable than air.To compare 24 common gases as potential atmospheres for aerodynamic tunneling,an equation is derived for gas efficacy,a function of the first power of the speed of sound and an inverse function of the first power of friction drag on an idealized flat plate.The higher the efficacy,the more the gas increases the Mach 1 speed or reduces drag.Hydrogen has the highest gas efficacy.Ammonia,hydrocarbon gases,and helium have above-average efficacies.Neon has the lowest.