At this week’s Farnborough Airshow, airline-rating service Skytrax announced the results of its 2016 World Airline Survey, rating more than 200 of the world’s airlines from best to worst. The rankings were based on responses to 19.2 million customer surveys.

Skytrax boasts that it uses sophisticated data-weighting algorithms to compensate for different sample sizes, and has fraud-detection mechanisms in place to maintain the results’ legitimacy. And the research is not funded by any of the ranked companies.

Still, although the survey is clearly more rigorous than most, there are questions about its methodology. It’s not clear, for example, how much weight is given to the various factors that, taken together, give an airline its overall score. Full transparency is reserved for airline executives, who presumably pay for privileged access to the full survey results.

The top-20 airlines, according to the latest survey:

1. Emirates
2. Qatar Airways
3. Singapore Airlines
4. Cathay Pacific
5. ANA All Nippon Airways
6. Etihad Airways
7. Turkish Airlines
8. EVA Air
9. Qantas Airways
10. Lufthansa
11. Garuda Indonesia
12. Hainan Airlines
13. Thai Airways
14. Air France
15. Swiss
16. Asiana Airlines
17. Air New Zealand
18. Virgin Australia
19. Austrian
20. Bangkok Airways

Given Skytrax’s global focus, it shouldn’t be any surprise that U.S. and Canadian carriers fared badly. Ranked among themselves, the top-10 North American carriers were as follows:

1. Virgin America (25th overall)
2. Air Canada (31st)
3. Delta (35th)
4. Porter (47th)
5. WestJet (50th)
6. JetBlue (53rd)
7. Alaska (60th)
8. Southwest (66th)
9. United (68th)
10. Hawaiian (72nd)

At the very bottom of the 100-airline list is the Indian low-cost carrier SpiceJet. And off the list completely is North Korea’s state-owned Air Koryo, the only airline to receive just one star in the Skytrax rating system, which awards a maximum of five stars. “The 1-Star Airline rating represents a poor quality of Product delivered across the assessment sectors, combining with low and/or inconsistent standards of front-line Staff Service for the Onboard and home-base Airport.” Kim Jong-un declined to comment.

Reader Reality Check

Are the Skytrax results consistent with your own assessment of the world’s best airlines?

After 20 years working in the travel industry, and almost that long writing about it, Tim Winship knows a thing or two about travel. Follow him on Twitter @twinship.

This article first appeared on SmarterTravel.com, where Tim is Editor-at-Large.