AirAsia achieved the highest score in Aviation Week’s latest Top-Performing Airlines (TPA) study, underlining the dominance of smaller and niche carriers in this year’s rankings.

Of the top 10 carriers overall, only one – Singapore Airlines in ninth position – comes from the category of airlines with annual revenues greater than $6 billion. Three are from the mid-size tier with revenues between $2 billion and $6 billion, and six have revenues of less than $2 billion. In every region, the smaller airlines are upstaging the giants.

Scores were generally down in this year’s study, with only 15 of the 71 ranked airlines achieving a year-on-year improvement. This was particularly evident in the large airline category, where just one of the 21 carriers – All Nippon Airways – registered a score increase.

Financial and operational data were analyzed to rate airlines in five different performance categories, from which the total score was derived. Wherever possible, data from the latest full fiscal year were used. Only publicly-traded airlines are included in the TPA study, which rules out the large Gulf carriers.

A common scoring system allows airlines to be categorized by size or region. Singapore Airlines (SIA), with 70 points, was the top-scorer in the large category for the seventh time in eight years. Ryanair was the leading airline in the mid-size tier with 78 points, and AirAsia was the best in the small segment as well as the top-scorer overall with 81.

The Asia-Pacific region saw the greatest contrast in fortunes between the majors and the smaller carriers. While it was the strongest large airline, SIA’s score plummeted by 23.8 points compared to the previous year’s study. Cathay Pacific has also traditionally been one of the best performers, but it declined by 20.4 points and fell to seventh in the large segment.

Remarkably, Malaysia accounted for both the overall top-scoring carrier, AirAsia, and the lowest-scoring, Malaysia Airlines. Garuda Indonesia was the biggest improver amongst all airlines, as its expansion plan gathers momentum.

Copa was the highest-ranked of the Latin American airlines by a wide margin. In Europe, Ryanair was first, 18 points above the best of the major carriers, Lufthansa.

The dominance of the smaller carriers was again evident in North America. Allegiant was highest-rated in the region, followed by WestJet, Alaska Airlines, and Spirit Airlines. Southwest was sixth in North America, and United was the best of the U.S. legacies at ninth.

The top 10 scores overall were: AirAsia, 81; Air Arabia, 78; Ryanair; 78; Hainan Airlines, 77; Allegiant Air, 77; TransAsia Airways, 72; Vueling Airlines, 72; Copa Airlines, 71; Singapore Airlines, 70; and WestJet Airlines, 69. The highest possible score is 99.

Click here for more information on the Top 10 Top-Performing Airlines 2012 in an interactive presentation.

Full rankings lists, expanded commentary and analysis, and a breakdown of the methodology are available to Aviation Week Intelligence Network subscribers here.