A computational investigation of flutter onset and limit cycle oscillations of the F-16 fighter using a nonlinear frequency-domain harmonic-balance approach is presented. In this latest study, we examine the sensitivity of computed aeroelastic behavior to characteristics and parameters of the structural and fluid dynamic model. Three different F-16 weapons and stores configurations are considered. Results indicate that the flutter onset Mach number is very sensitive to the structural natural frequencies, and, more specifically, the difference between the natural frequencies, of the first two antisymmetric structural mode shapes. Wing mean angle-of-attack is also shown to be very important. The results presented herein may prove useful and provide insight to other researchers modeling F-16 fighter aeroelastic behavior, and who also may be observing large sensitivities in their computational solutions.