Depends on how nice and how you want things to be handled.
You could either make him pay for it all, stating that if you want to see your son, you pay to fly him out. or else you could split it (so each person pays one way) and share the finical responsibility of it.
So unless you went to the courts and made them determine who had to pay, you two need to work this out. It sounds like you have done a great job figuring out things on your own on how to handle things, so this shouldn't be any different.



