Southwest, United, and JetBlue top the domestic carriers, according to a survey by consulting firm IdeaWorks. At the bottom are Delta and US Air, which had no seats available on at least two out of every three inquires. As you can see from the chart below, international carriers have some of the best programs. The survey points up an interesting trend: Proportioning points on factors other than straight miles traveled. From the WSJ:
Carriers with programs based on points tie rewards to dollars spent rather than miles traveled. Higher fares earn more points--so coveted business travelers are well rewarded. And travelers can find seats when fares go higher without blackout dates or capacity controls--the price in points goes up proportionally with the price in dollars. Conversely, when airline programs award miles based on the distance traveled, higher fares often don't get higher rewards. And many flights don't have seats available at standard mileage levels, such as 25,000 miles for a domestic round-trip, which leaves many consumers frustrated. Several carriers, including Southwest and JetBlue, have converted their programs to points, and more are expected to convert in the next couple of years.