Three-day sales are apparently all the rage this week, the newest entry coming from Frontier Airlines, good for noon Monday-noon Thursday travel through May 20. Fares do require a 14 day advance purchase and all purchases must be made by January 23.

Upgrades from 'Economy' to 'Classic' start at $20, and to 'Classic Plus' for $50.

Beware of the following blackout dates: February 13, 16, March 6-8, March 13 - 15, March 20 - 22, March 27 - 29, April 3 - 5, April 10 - 11, and April 13.

For further details, visit FrontierAirlines.com, and check your city page for fares.

United Airlines lost $1.3 billion in the last quarter, and announced 1000 further salaried and mangement job cuts in addition to the 2500 job losses announced in Q2 2008. In additon, the nation's third largest carrier (after American and Delta) will further downsize, parking aircraft and reducing seat capacity. Airline ticket purchases continue to decline, despite some really amazingly low fares, as the economy deteriorates.

Some industry watchers suggest that further downsizing and consolidation is inevitable. One thing that's preventing future consolidation is that the remaining players are still too big to get government approval for a merger (e.g., if United and US Air were to combine at their present sizes, the new entity would have too large a market share to suit antitrust regulators and Congress). But what if those carriers continue to cut personnel, seat capacity, and routes? Then they' might "right size" to the point where a merger would be possible. Anyway, that's the thinking of some in the industry. No predictions here about whether that will come to pass.

But airline shrinkage is a fact of life. American Airlines also reported dismal financial results for the quarter just ended, with a $340 million loss. American plans to cut total seats flown by 7 percent this year compared to last, while United plans to eliminate up to 12.5 percent of capacity in North America in 2009 and 5 to 6 percent internationally, for a total full year reduction systemwide of 7 to 8 percent.

Yep, WestJet is having a 1-day 50% off sale, good for travel on Mondays, Tuesdays, and Wednesdays, through April 8. This sale expires at midnight tonight, so get movin'! Check out WestJet.com for more info.

Southwest has launched a three day 50% Off sale to/from Seattle Tacoma, good for travel between February 3 and May 31. All tickets must be booked by midnight, January 22, and only on southwest.com, using the following promo code (quick, grab your mini golf pencil!): SEATTLE

Got that? Super! Now go take a look at our Seattle fare page (To Seattle or From Seattle, you choose).

On a related note: Now we're gonna have this song stuck in our head for the remainder of the day. So, yes, thanks for that, Seattle sale.

*****Update, as of Wednesday morning: Northwest, United, and Delta have now entered the ring, and with fares even lower (in most cases) than the Southwest 50% off sale:

• Baltimore to Seattle $96 round-trip
• Birmingham to Seattle $96 round-trip
• Charlotte to Seattle $151 round-trip
• Columbus to Seattle $86 round-trip
• Ft Lauderdale to Seattle $115 round-trip
• Hartford to Seattle $96 round-trip
• Philadelphia to Seattle $114 round-trip

Check our Seattle fares page for the complete list of today's fares.

In all our years of watching airfares, we hadn't seen a sale to Europe for spring and summer travel quite like this.

Launched on a Saturday (Jan. 17 to be exact) over a holiday weekend (which is typical), this was an extensive sale between large and small US cities served by US Air to several, but not all, major European capitals. Fares were approximately $300-700 less than competitors' prices, and surprisingly not a single competing airline matched.

Another point I want to make: If you had signed up for an airfare alert based on price only, you might have missed these bargains. That's because the lowest fare between, say, Harrisburg and London didn't necessarily go down during this sale. What went down were the time of year travel restrictions. Suddenly, a winter $600 RT fare was now a summer $600 RT fare. So let's say you signed up with Travelocity or Orbitz to alert you if the fare on that route went down. Since it didn't go down, you'd get nada.

Oddly, too, I didn't see this sale mentioned on any travel media Web site (except ours, of course). Maybe the other guys don't work over the weekend (there were a lot of great football games after all). Unfortunately for me, but fortunately for our readers, I usually work weekends and holidays because I  know that's often when the really good fare stuff happens.

Of course, many of our readers don't open email over the weekends or on holidays, so they'll be opening old emails and clicking on fares that no longer exist. Sorry 'bout that. Will we see fares like these again this summer? Perhaps, but somehow I doubt a new sale will be as wide ranging as this one.

A few summers ago, Virgin Atlantic had an amazing summer sale to London, but it was only on the routes they served. And we have seen sporadic, targeted sales to Europe in the past. So who knows. We'll keep you informed.

As some of you may know, Airfarewatchdog.com is a division of SmarterTravel.com, which itself is a part of the Trip Advisor family of web sites, which in turn is owned by Expedia. So we were on the one hand very proud when staff writer Molly Feltner at Smarter Travel, fierce believers in editorial independence that they justifiably are, wrote today that "Farecast's alert service is the most reliable such tool out there."  Of course, on the other hand, we strongly believe that we're a pretty darn good fare alert service, too.

After all, Farecast doesn't track Southwest's fares, we do; Farecast doesn't track Allegiant Airlines's fares (can you believe how fast they're growing these days?) or little airlines like DirectAir; we do.

Farecast doesn't include promo code fares, such as Southwest's recent 50% promo code sales, or JetBlue's frequent 10% off deals; we do.

Farecast doesn't send out alerts on Spirit's 1 cent sales; we do.

Farecast wouldn't show you that spring and summer fares to Ireland and other European cities right now on Aer Lingus are $50-$100 cheaper on aerlingus.com than they are elsewhere, or tell you that many other airlines offer signficant discounts if you book on their own sites rather than on an Orbitz or Kayak; we would.

And, although Farecast is in the business of prediciting fares, they sure didn't predict that fares to Europe would plummet 50-60% this past Saturday (in fairness, who could have predicted that?); we sent out alerts about these fantastic bargains as soon as our little fingers could type.

Now, don't get us wrong, we think Farecast is a useful site; it's just that we do some things better than they do, and we just don't think they're any more "reliable" (whatever that means) than we are, or, indeed, than Yapta or Farecompare are. All three sites use ITASoftware fare data, so really they get their fares pretty much from the same place. They just slice and dice and data in their own unique way.

Anyway, if you're a fan of ours, feel free to comment at the bottom of Molly's article. I know I will!

Update: We contacted Molly and it turns out she hasn't been subscribing to our fare alerts for a while, so we took the liberty of signing her up. Maybe she'll rediscover the value we offer!

For whatever reason, the airlines have eliminated advance purchase restrictions on their  lowest fares to St. Thomas, San Juan, St. Maarten, and perhaps a few other destinations. The fares are low, and you can pack and go!

Lowest fares are for travel Mon-Thu.

St. Maarten

St. Thomas

San Juan

UPDATE JAN 20: THIS SALE APPEARS TO BE HISTORY

Amazingly, the sneak holiday weekend unadvertised sale to Europe on US Airways continues, and equally amazing, no other airline has matched. Fares to Rome are in the 500's and 600's RT including all taxes for travel in April and early May (and probably in March, depending on the route).

See the fares we've found to Rome.

US Airways has just launched a fantastic sale for spring travel to Brussels from many US Air cities. Fares are up to 50% less than other carriers are charging, in some cases even less!  In general, these fares are in the 400's, 500's and 600's RT, including tax. Some airlines are charging $1200, $1300, even $1400 right now. In general, these fares are available for travel in April and May. Brussels is in the heart of Europe and it's easy to get anywhere else in Europe from there.

This is part of a much larger US Airways European sale for spring and summer travel.

Check out our international fare search for details.

We'll update this as we research more fares, but it looks like US Air is having a sale, at least on some routes and at least for August travel, to London and Paris. Service is from many cities, including some you'd never think of, such as Spokane, WA and New Haven, CT! But also from larger airports as well.

Update: We're now finding scattered fares in the 500's incl. tax from various cities, including many smaller airports, to Amsterdam.

Fares are in many cases at least half of what others are charging. Some are even bigger discounts.

And as usual, the fares make no sense geographically. Seattle to Amsterdam is $520 RT including tax; Boston to AMS is $579 RT.

So if you thought Europe was out of reach this summer, think again....and remember, the Euro is way down vs. the dollar, compared to last summer. Use our international fare search to see fares.

Update: Some of these fares are only available for mid to late August and September travel; some are also available for June travel.

Update: Looks like Shannon is also on discount, and there are a few fares to Manchester and Glasgow. We also found Seattle to Brussels in May/June on sale, but not in summer.

Update Sun Jan 18: these fares are still available, although with fewer seats and dates. Surprised that other airlines are matching, but perhaps they don't need to. However, US Air appears to have added new routes... so shop around.