The present invention is an air injection collar for use in the drilling industry that is used to reduce the weight of the column of returning drilling mud and debris without causing unnecessary frictional wear on the drill pipe. The invention is a unique sleeve that is coupled to a drill casing that includes an input port for receiving the pressurized air or other fluid from the surface, an annular plenum extending around the drill casing, and a series of openings in the plenum leading to the inside of the drill casing. These openings disperse the pressurized air or other fluid into the upflowing mud around the central drill pipe so that it is not concentrated in one place, especially the center of the casing, where it could cause frictional damage to the drill pipe.