I am thinking of purchasing a new 2.4 ghtz transmitter and would like to know if there is any compatibility between brands. Hitec and Airtronics use the same "AHSS" designation for their spread sectrum systems but would a Hitec tramsmitter bind to an Airtronics receiver and vice versa?

Unfortunately, no. All these are patented and they encode and decode differently. They might be called the same cause they use the same concept, like DSSS, but the inner workings are not the same.