Abstract: In order to predict the aircraft stability'at high-angles-of-attack,some criteria were suggested and cnB.dyn is one of the most important criteria. Some surveys.about correlations of CnB.dyn with flight tests and authors opinion, the divergence can be predicted in most cases when Ca.dyn is negative. An example is'given to explain the effects of some of the aerodynamic derivatives on the aircraft stability.These derivatives are connected with GnB,dyn. Time history studies are carried out in this paper by programming, on a digital computer, a set offequations of motion pertinent to a typical fighter,by varying some of the aerodynamic derivations in a prede-terminate manner, and by observing the responses of some of the variables of mot ion to derivatives applied to the set of equations. From the calculating results, we can see that the aircraft could be unstable at high-angles-of-attack even the criterion is still satisfied, In the last part of this paper, we try to give some reasons to explain why these exceptions do exist.