Legroom: It's perhaps the most important metric in the quality of your flying experience, and it's one you usually won't know until you climb aboard: Everything either feels cramped or kind-of OK. Airlines use different planes on different routes, and each one will have different specs.
Proactive travelers can take a look at websites like Seatguru for advisories — but as a shorthand, consider this Skyscanner survey of the airlines offering the best and worst legroom. The winner? WestJet, with economy seats offerings 31 to 38 inches in pitch. Do you love poutine? Hockey? Moose? Free entry to national parks? Then you might love WestJet. On the other side of the scale, we have China Southern and Thomas Cook, which supply between 29 to 33 and 29 to 31 inches in seat pitch, respectively.
Many airlines come in with a minimum of 31 inches, including Virgin America, Delta, British Airways, Norwegian, and Qatar. Cathay bumped standard economy seats to 32 inches, as did Jet Airways. Reader beware: The survey did not include some big carriers, including American and United. For the full results, see here.