Defining how/what flights are allowed per a given quota is purely under HMGs remit, not ICAO

There were great strides in the QC system in terms of reducing pollution/noise and driving airlines to operate more modern aircraft in the 1990s/early 2000s, not so much recently. In fact, they only banned RR 747-400s during the pandemic, just after BA decided to remove them from their fleet.

Allowing 40 year aircraft to fly into Heathrow in the 2030s is ridiculous.