Most airline HQs have historical links even if they don't have bases there any more.
BA Citiflyer were BA Regional, which was born, if not concieved as a Manchester base, even if Mummy and Daddy were from London.
Jet2 are close cousins of Channel Express and lived in adjoining Council Houses as youngsters in Bournmouth before Uncle Philip spread his favours
.
Suckling Airways were concieved and born in Cambridge, grew up went to Junior School and the first two years of High Schol there, when along came Scot Airways with the usual Scottish foreplay and adopted them as Mc Cousins.
TUI, as far as I know, have always operated from office buildings, their Ops for the entire fleet, as far as I know, are based in a huge underground bunker in Hamburg.
Monarch are one of the few airlnes that have always been faithful to the cause and always have been based at Luton Airport.