Travelers may find it just a teeny-tiny bit easier to redeem miles this year compared with last year, according to a new study of 24 different frequent-flier programs world-wide.

Best among U.S. carriers: Southwest Airlines Co., which had award seats available for 99.3% of the queries made, and jetBlue Airways, which offered seats 79.3% of the time. Southwest and jetBlue both use points instead of miles, and IdeaWorks Co., the consulting firm that conducted the study, searched for award seats available at 25,000 points, the...