A third Heathrow runway
Why? The solution most in aviation favour. Bar the politics, the most deliverable option, to be funded through private investment.
Why not? Puts another swath of west London directly under a flight path, and blights thousands more. Transport secretary Justine Greening stood against it – and lost her job in the cabinet reshuffle earlier this week. Some argue – even Willie Walsh, boss of British Airways' parent company IAG, concurs – it's not a long-term answer to a lack of hub capacity, an airport big enough for connecting flights that make long-haul services feasible.
Combine with Gatwick
Why? Connect the two biggest London airports with a high speed rail link and voila, a super-hub, "Heathwick". Second runway plans are drawn up; there are fewer people in the vicinity.
Why not? A train ride too far for transfer passengers, so would not deliver the solution to the hub question. Any movement ruled out until 2019.
A second Stansted runway
Why? The best option according to Ryanair boss Michael O'Leary, who believes that when BAA sells it and new owners invest, the fall in passenger numbers will be reversed. It's in Essex, not on the edge of prime west London real estate. There's more space for expansion.
Why not? Poor connections to London. Without major investment in all the infrastructure and a shift in its low-cost reputation, its appeal will continue to dwindle.
Boris Island – a Thames estuary airport
Why? The most advanced of all proposals, with a blueprint from Norman Foster. It would, says Boris Johnson, revitalise east London and deafen fewer people.
Why not? Revitalise the east, yes, and destroy the west by closing Heathrow. Risk of bird strikes. Lack of infrastructure. Unexploded bombs on the nearby sunken SS Richard Montgomery. Plus if Boris swings this, he'll be PM.
Another new hub in the home counties
Why? More accessible than the estuary. Rumours Oxfordshire is under consideration. An ancestor of the Howard Davies commission, the Roskill commission, concluded in 1971 that Cublington, Buckinghamshire, was the best place. Government ignored that one too.
Why not? Enormous bill, decades of work, Nimby central.
A bigger role for regional airports
Why? The likes of Birmingham have plenty of spare capacity. If aviation brings benefits, why not spread them? Would save people from chugging down the motorway to Heathrow.
Why not? As Heathrow boss Colin Matthews likes to point out, if airlines wanted to fly to Birmingham, there's nothing stopping them. Government can't artificially create demand.
Do nothing
Why? Constrain demand and you'll get less noise, cleaner air, a less rapidly melting Arctic ice cap, and fewer votes lost in west London marginals.
Why not? People will still fly, just via hub airports in Europe. Britain will lose the economic benefits and the CO2 will be pumped out regardless.
