Finding Comparable Companies

Hey guys, I am trying to value a private company. As a first step, I would like to try to find comparable companies. The thing is that the company in question is a software company that sells scheduling software to airlines. So quite a niche area. What do you think is the best way to go about trying to find comparable companies?

Phone airlines and ask them whose software they use. Tell them why you’re doing so, lest they think that you’re a salesman.