I am considering the A319, A320 and A321 to all be different, but the 737-300, 737-800 and 737-900ER to all be the same.
I'm not too sure what you mean. Is it 737-800s only, since you omitted the A319 and A321?
- Transavia, both HV (NL) and TO (FR).
- Blue Air.
- Comair/Kulula and FlySafair (South Africa).
- Eastar Jet.
- In China: Shandong, OKAir, Ruili, Urumqi, off the top of my head.
Most of these have other 737 variants than the -800. A bunch of them still have 737 Classics. Some have completely different types, like SunExpress' A330s and Urumqi's ARJ-21s.
It seems the A320 should be compared only against the 737-800 and not any other type of 737, in which case I am wrong to talk about other 737 variants. I stand corrected. My flawed logic was that the A319, A320 and A321 have different numberings for different seat capacities, but with the 737, since all variants use the same 737 name, seat capacities could be disregarded.
Unfortunately the first post cannot be edited any more. Still I will have to remove the airlines you listed, and Blue Air specifically, because most of its 737s are very old.
However, the main SunExpress in Turkey operates only 737-800s. The SunExpress that you are talking about is the German one, which operates the A330 for Eurowings, and in EW livery.
Yes but why - I'm not sure what it's meant to achieve?
Just taking Sriwijaya Air as an example, the 'type' B737 covers variants from the 120 seat -500 right up to the -220 seat -900ER. There is no meaningful comparison if you are only considering the A320.
Also in Europe I can think of Air Corsica, BH Air, Bulgarian Air Charter (MDs are now parked IIRC), Freebird, Orange2Fly, SAS Ireland, Smartlynx Estonia and TCX Balearics.
Indeed, the airlines you mention here are very small, barring SAS Ireland and to an extent Freebird. The Vuelings and Wizzes of Europe all have A321s, though they started out with only A320s. However, Air Corsica has ATRs.