Most decent length operating agreements of this sort would end up with annual inflator(s) under inflation, under competition (eg. x -.75% or whatever). The expectation being, given a fair run, a quality organisation will sustain continuous improvement.

Quite why Heathrow got away with inflation+ in the past eludes me.

As I understand the position, LHR has a very high passenger throughput, yet is also very close to top whack charges per passenger amongst world airports.

There's a lot to like about HAL's plans, this formula does I think give them more money, so its really over to them to put away the begging bowl and get on and deliver value.