They can buy the lease which is what I think Stobart’s did. It has been argued that the Ltn deal was too good for the council as it could have impacted investment.
With the Southend deal the council is getting a minimal sum per passenger which decreases as the passenger figure goes up so the council do not get to share the airports success despite ultimately still owning it. No doubt it might have been seen as a good deal at the time but not any more.