Turbojets with thrust not exceeding 25 kN fall under 841111; those exceeding 25 kN fall under 841112. The manufacturer's type certificate or technical data sheet stating the rated static thrust at sea level is the standard supporting document. For engines with variable thrust ratings, the maximum rated thrust is typically used.

APUs that function as gas turbines — producing shaft power or bleed air through combustion — are generally classified under 841181 or 841182 depending on their output rating, rather than under the turbojet or turbopropeller subheadings, since they do not provide propulsive thrust. Confirming the classification with a binding ruling is advisable given the high unit values involved.