My co-founder and I have a combined 20+ years of experience in the airline software industry. When we set out to start our own business, it was clear that we were not going to sell to airlines. Too many legacy systems, too much historically grown cruft, needless complexity, too many individual requirements but no money to pay for it. Plus they're distributed all over the world so selling to them is very costly. It's a shame because we would have had a big head start in terms of domain knowledge.