With "knowledge" only going back to Sept. 2021, still a helpful list. Produced in seconds, may contain inaccuracies.
By approximate fleet size.
Turkish Airlines (Turkey) - Approximate fleet size: 350+
Lufthansa (Germany) - Approximate fleet size: 280+
British Airways (United Kingdom) - Approximate fleet size: 280+
Air France (France) - Approximate fleet size: 220+
KLM Royal Dutch Airlines (Netherlands) - Approximate fleet size: 120+
Iberia (Spain) - Approximate fleet size: 120+
Scandinavian Airlines (SAS) (Sweden, Norway, Denmark) - Approximate fleet size: 120+
TAP Air Portugal (Portugal) - Approximate fleet size: 100+
Swiss International Air Lines (Switzerland) - Approximate fleet size: 80+
Finnair (Finland) - Approximate fleet size: 80+
LOT Polish Airlines (Poland) - Approximate fleet size: 80+
Austrian Airlines (Austria) - Approximate fleet size: 80+
Aegean Airlines (Greece) - Approximate fleet size: 60+
Royal Air Maroc (Morocco) - Approximate fleet size: 60+
Brussels Airlines (Belgium) - Approximate fleet size: 50+
Aer Lingus (Ireland) - Approximate fleet size: 50+
Virgin Atlantic (United Kingdom) - Approximate fleet size: 45+
Ukraine International Airlines (Ukraine) - Approximate fleet size: 40+
Widere (Norway) - Approximate fleet size: 40+
Air Baltic (Latvia) - Approximate fleet size: 25+
Icelandair (Iceland) - Approximate fleet size: 25+
Tarom (Romania) - Approximate fleet size: 20+
Enter Air (Poland) - Approximate fleet size: 20+
Blue Air (Romania) - Approximate fleet size: 20+
Luxair (Luxembourg) - Approximate fleet size: 20+
Bulgaria Air (Bulgaria) - Approximate fleet size: 10+
Air Corsica (France) - Approximate fleet size: 10+
Air Malta (Malta) - Approximate fleet size: 10+
Air Dolomiti (Italy) - Approximate fleet size: 10+
Air Greenland (Greenland) - Approximate fleet size: 5+
Air Iceland Connect (Iceland) - Approximate fleet size: 5+
Montenegro Airlines (Montenegro) - Approximate fleet size: 5+
Aurigny (Guernsey, Channel Islands) - Approximate fleet size: 5+