Directional-repulsorlift steering was a specific kind of engine suitable for use in air buses. A study conducted by the Rhire Medical Academy in 13:3:28 identified multiple species on the planet of Coruscant as vulnerable to disease as a result of air pollution; consequently, the study suggested substituting older air buses that utilized propellant-based lateral thrusters with newer models that employed directional-repulsorlift steering.