Never buy a supersaver ticket when arriving by aire. Buy a regular ticket or if it is cheaper buy a saver day pass.
A regular ticket is good for a single trip on the route you bought it for, but is valid a whole day, so you can just use it on any departure convenient to you. This is what you buy when you buy the ticket at the station just before travel. And that is what most people get here.
A saver day pass is good for all the public transit in the country, for a whole day, and thus will permit you to reach your destination regardless of where it is…