Approach operations to Heathrow are constrained by
inter alia the Cranford Agreement.
An increase in capacity would be achieved by allowing independent mixed mode ops on both the north and south runways. Another capacity gain would be an extension in the hours of operations; even allowing low QC numbered a/c to land later/earlier might help.
A third runway could accept appropriate a/c from existing stacks. RNAV (GNSS) SBAS APV operated to RNP 3' 6" would be the enabler.
Lastly 4D trajectory flight management would help dovetail arrivals with stand availability.
"Ladies and Gentleman, due to favourable tailwinds over the Atlantic I'm pleased to tell you that, despite our departure from (K*** or C***) being 15 minutes behind schedule we'll have you at destination 45 mins early"
"Ladies and Gentlemen, as you will no doubt have noticed we are currently in a stack to the west of London. This is due to ATC delays caused by early morning congestion. So sit back and enjoy the rest of the flight."
Ladies and Gentlemen, from the flight deck may I add my warm welcome to London Heathrow. Due to the outbound a/c on our stand not quite being ready to depart we have been asked to wait here for a few minutes. Therefore I'd ask you to remain seated until the fasten seat belts sign is turned off. Crew, thanks for a wonderful flight, cabin doors to Manuel and cross dress."
Ladies and Gentlemen, as we pull onto stand can I repeat my welcome to London where the local time is 09.15 our scheduled arrival time. Thank you for choosing to fly BA (even though there's no-one else on this route) and wish you a very good morning."
Well Nigel, that went well don't you think? Yes boss, but if we'ed adjusted our flight to arrive on slot we would of used 3 tonnes less fuel.
SGC