Aircraft are provided with a pair of auxiliary power units (APUs) adjacently mounted in parallel relative to one another within the tail cone section of the aircraft's fuselage. In some embodiments, the APUs are mounted generally vertically adjacent to one another. Alternatively, the APUs may be mounted generally horizontally adjacent to one another. The aircraft fuselage may include a pair of downwardly and outwardly oriented strakes adjacent the tail cone having lower edges which establish a maximum take-off pitch angle of the fuselage and define a spatial zone therebetween. The APUs are positioned within such a spatial zone defined between the strakes so that the maximum take-off pitch angle is not required to be changed when modifying an existing single APU aircraft with dual APUs.