Airlines come and go (many literally), but by and large are quickly replaced by others :-
Qantas - dropped all of Europe (except LHR) when they jumped into bed with Emirates. QF probably sell more seats from MAN today on the 3x daily EK flights than they ever did on their own metal.
SAA - busily self destructing under the weight of corruption and better competition, nowadays barely able to maintain an A330 service to LHR
Gulf Air - relegated to a bit player when its key shareholding states decided to form their own airlines. Emirates, Etihad, Qatar and Oman now rule the ME skies
Cubana - was a short lived pseudo tourist flight (or was it a tech stop ?). Long since replaced by much better and higher capacity offerings to Cuba from TCX and TUI.
MALEV and LOT - both done for in the UK by Ryanair, Jet2, Easyjet, Wizz - as were most state owned East European airlines
A glance back at a MAN timetable from just 10 years ago shows just how quickly the industry evolves. Airlines featuring then included Sky Europe, Czech Airlines, BMI, Air Berlin, Zoom, Continental, City Airlines, VLM, Hapag Lloyd Express, Air Blue, Cyprus Airways, BA metal to JFK - to name but a few. All now gone, but always replaced in one form or another.