No. Why should I?
There are times when I don't understand why a person would choose a competitor, but it doesn't make me angry or bitter. I just don't understand.
No. At least they shouldn't.
Here's another one of the important lessons I've learned with business: Nobody cares about you. It sounds harsh, but it's the truth. Your customers don't owe you anything. It doesn't matter if you're running a grocery store, car wash, FBO, flight school, or any other business. The fact is, you're running a business, not a charity. It's great if you have loyal customers who want your business to succeed, but you shouldn't, and can't, depend on their goodwill to keep you alive.
It's not reasonable to expect people to keep using your services if you're inferior to your competition. In the case of an FBO/flight school, that could be any number of things. Aircraft types available, quality of aircraft, availability on the schedule, quality of instructors, rental rates, location, the list could go on.
For instance, you can't expect a customer to put up with delays because you're short staffed and working really hard. That doesn't matter. It's not the customer's problem. They aren't obligated to stick with you just because you seem nice, or are trying to keep the business around in tough times, or whatever. Being nice isn't enough. The bottom line is that if the customer can find better options elsewhere, they should go there.
It's the owner/manager/employees' job to make sure there are no better options. If their customers start leaving, they shouldn't get mad at the customer, they should figure out a way to improve their operation so that customers have no desire to leave.