If a cohen cancels his flight schedule because on his flight there is going to be a deceased person, and he has to buy a new ticket which is much more expensive for a last minute ticket; who is responsible to pay for his loss:
a) himself, because the deceased family is buying a legal ticket and transport for the deceased, or b) or the family of the deceased because they know that by transporting a deceased, a cohen will have to cancel his ticket on this flight and buy a new ticket.
The Cohen has to incur the loss. He should have checked up with the airlines before purchasing the ticket if their policy is to transport coffins, not all the airlines agree to do it. Perhaps if you inform the airline that the ticket change was due to religious reasons they might be more understanding of the circumstances.