In support of full-electrification of aircraft and of aircraft design in general, detailed modeling of the aircraft electric generator is very useful. High-fidelity modeling of high-speed generators is necessary for the development of all-electric aircraft. Nonlinear magnetics play a significant role in the transient behavior of a synchronous machine (SM) generator during load on and load off cases. This paper demonstrates the nonlinear magnetics of an SM generator and nonlinear functions that accurately fit the magnetics.