Earning miles has always been easy. But redeeming miles is not. Award Wallet estimates that some 10 trillion frequent-flier miles in circulation today, worth well over $165 billion, have gone unused. You might think you need 50,000 plus miles to book a trip, but JetBlue offers round-trip tickets to select vacations destinations at air mile rates as low as 10,000 miles. Other airlines sell round-trip tickets for a bit more miles, but offer in-demand destinations like Hawaii, Jamaica, and Cancun.

The good news is that it’s getting easier to redeem your miles. Reward availability on airlines continues upward with 2012 results 5 points higher than 2010, according to the 3rd annual Switchfly Reward Seat Availability Survey, released recently by IdeaWorks. The study confirms that frequent flier programs have been  improving member rewards. Nine airlines scored above 80 percent availability for 2012, which is much improved from five airlines above 80 percent in 2010. Among the larger US-based carriers, United Airlines’ Mileage Plus program offered 87.5 percent availability, the highest among the carriers. Next up was American Airlines, then US Airways. All three airlines delivered results above last year’s survey, but Delta Airlines’ award seat availability has dropped.

Now, once you’ve banked 25,000 miles you have the option for some pretty stellar round trip tickets. The key is to know how to make the programs work for you. Read on to discover the best trips from American Airlines, United Airways, JetBlue and Delta that you can book for 25,000 miles round-trip.