Ah, don't expect a refund.
>> 1. Nearly all airline ticket taxes apply as of the date of sale of the ticket rather than as of the date of the flight. Thus, if the government raises a tax or levies a new tax after you buy your ticket, you are not liable -- but, conversely, if a tax expires or gets reduced after you buy your ticket, there's no refund.
>> 2. And in any case, all of the the airlines raised their fares by the amount of the tax that expired when one of the taxes on airline tickets expired recently. (In the past, they typically have lowered their fares by the amount of a tax hike when the government has raised taxes.)
So the bottom line is that there's no change in what you pay. All that changes is where the money goes.