Been flying with 135 operators for nearly 40 years and have never heard of anyone tipping them. Maybe I needed to listen better.  The cost of bush flying is very high already. I need to check this aspect of flying out. Most of the pilots do a good job. But they are under pressure from their bosses and the public to fly in just about any weather conditions. And if they turn down a flight they are subject to being replaced by someone who will take the flight. Passengers have a responsibility to use common sense also.  Ask if the weather is safe for flying or if the plane is overloaded. Don't go if you believe it is not safe to board. Remember it is always better to be on the ground wishing you were up there rather than being up there wishing you were on the ground.