"Booking & Ticketing Policies of SWISS" (PDF). SWISS International Air Lines Ltd. 20 May 2014. Retrieved 13 July 2014.
While it is not clear if carriers should refund users regarding navigation taxes (related to the airline operation and to the governments, which do not appear on a ticket), other expenses, like security, air passenger duty, and noise/environmental can all be refunded, as these all relate to the passenger's use of any particular airport to depart/arrive on any particular flight.
This clause has raised much concern among users, and court rulings have converged to the conclusion that "carriers cannot force passengers to fly".