Spirit Airlines is not the only carrier offering $9 fares these days: JetBlue has jumped into the act, offering “cheeps” through their twitter feed (and available on their website on Monday mornings). Fares are generally just for the following Saturday (which is not the case with Spirit) and only for one-way in one direction. Yes, that’s pretty limiting. But this week’s $9 JFK – Washington DC fare, for example, could be combined with a $15 bus fare on the return for a fun day in DC. Other fares include Long Beach – San Francisco ($9), and Boston to Aruba ($49).