(ABC News / FareCompare.com) -- Travelers of all stripes have their own special acronyms. For drivers, it might be an old pal like AAA (American Automobile Association) or newer friend GPS (Global Positioning System). Both translate into helpfulness. Flyers should be so lucky.
Know what air travelers get with AA, DL and UA? Fly those airlines (American, Delta, United) with a single checked bag and you get a $50 fee.
But there are two acronyms that can help save money. Especially when shopping for plane tickets.
You may never stumble across these three letter codes, not unless you study raw airfare data like I do, but you don't need to see them to use them to your advantage.
1. Acronym: XFS
Not to be confused with FX (home of "The Shield," "Nip/Tuck," "Anger Management"), the acronym XFS is used by airline pricing geeks when discussing airline sales. Its meaning is simple: XFS = Excludes Fridays and Sundays. In other words, fly any day you want as long as it's Monday through Thursday or Saturday.
Here's why: Fridays and Sundays are the most popular days to fly. Leisure travelers love them because with a week-long vacation, it's the biggest-bang-for-the-buck, time-wise, plus it's when to fly on a "no vacation day" weekender. Business travelers may not be quite so fond of these days because it's just another working road trip, heading out Sundays, returning on Fridays. But airlines sure love these days; they can charge more.
And since carriers have no trouble filling Friday/Sunday seats, why offer a discount? They don't have to! And with XFS in the fine print, they let you know it.
TIP: You too must XFS -- exclude Fridays and Sundays -- if you want to save on your next trip.
2. Acronym: TWO
Do not confuse this with TOW (tube-launched, optically tracked, wire-guided anti-tank missile) or WTO (the international trade agreement organization). TWO = good for flights on Tuesdays and Wednesdays only.
What airline would offer such a limited sale? JetBlue for one, and here's why: Not too many people want to fly Tuesdays or Wednesdays but those seats must be filled and JetBlue does this by making generous discounting an art form. Last week it offered some Tuesday/Wednesday flights for a bargain-basement $39 one-way, and that was for peak summer season! Prices like that make it easy for passengers to overcome their distaste for midweek travel, and that's the point.
TIP: You too should try flying TWO because Tuesdays and Wednesday are almost always the cheapest days to fly in the U.S. (and this is often true on international flights operated by domestic carriers). The runner-up in the cheapness stakes is Saturday.
Okay, time for an obscure quiz. Translate the following: XFS SUX and TWO BFF.
No, it doesn't have anything to do with rude comments about best friends. The first part refers to sales that exclude Fridays and Saturdays in Sioux City (SUX, one of the weirder airport codes, is the designation for the Iowa town) and second refers to a sale good for Tuesdays or Wednesdays only to/from the Scottsbluff, Nebraska, airport. Now get out there are save on your summer trip.