Have you looked at the Allegiant Airlines route map lately? While other airlines are dropping routes, this scrappy low cost carrier is adding them. One of their latest cities is Grand Rapids, with nonstop service to Orlando/Sanford and St. Pete. With few exceptions, Allegiant connects smaller airports throughout the US to warm weather vacation and convention destinations, such as Las Vegas, Orlando, Mesa AZ (near Phoenix) and St. Petersburg.

Allegiant holds frequent "sneak" sales with fares as low as $15 each way, and constantly fiddles with its pricing, which certainly keeps us on our toes. Although they have many extra fees, most notably a $13.50 charge for booking online or $10 per segment by phone (no charge if you buy at the airport) their fares are consistently low, and the flights are almost all nonstops. Like Southwest, Airtran, and JetBlue, they also sell all their fares one way for half the round-trip price. And unusually, for $50 you can change the passenger name on a previously purchased ticket, so you can transfer the ticket if you can't use it.

Allegiant is also one of the few profitable airines in the US right now. They keep the bottom line healthy by selling vacation packages and ancillary services like shows (such as Blue Man Group), rental cars, and tours.

One thing to look out for when booking on their site: if you just want airfare and not a package, be sure to click the "Flight only" button on their booking engine. Enter your travel dates, and you'll automatically be shown a flexible date calendar showing which fares are available those months. Use the arrows to search subsequent months and you may find lower fares. We've found that they often launch their best sales on Saturdays.

Allegiant's fares do not appear on online travel agencies or fare aggregators, and are only sold on their own site or over their reservations line at 702-505-8888 (yep, it's not toll free). Airfarewatchdog researches and reports on their fares route by route seven days a week, 365 days a year.

Currently, Allegiant is accepting reservations through July 31, 2009. Sign up for their emails, since they sometimes send out promo codes that will clip a few dollars off of their regular fares.

And in case you were wondering, Airfarewatchdog has no monetary relationship with Allegiant. They don't advertise with us or pay us commissions. Heck, they probably don't even know we exist.