In July the independent Airports Commission handed the government a clear judgement and a problem.
According to Sir Howard Davies and his team the economic case for Heathrow was so compelling it blew its rivals away.
There were environmental challenges, sure, but although extra capacity at Gatwick was "plausible" it wouldn't deliver the same level of national prosperity
Now Sir Howard Davies says "things have changed" since the summer.
A reference, we're told, to the fact that Volkswagen has since admitted that 1.2 million of its cars in Britain have been fitted with software that cheats emissions tests and are therefore more polluting than advertised.
The government is in the process of establishing how big the gap between official emissions data and lab tests is but has decided the environmental impact of a third runway needs to be reassessed.
Fair enough but don't forget how problematic the politics are, not least for David Cameron who promised a promised a third runway at Heathrow wouldn't be built "no ifs, no buts" before he became prime minister.
More generally, the government has a pollution problem. Heathrow breaches legal air quality limits set by the EU, so to do all but five of Britain 43 emissions zones.
The government has been taken to court and has lost. It now has to spell out how it plans to reduce nitrogen dioxide emissions. It has decided that the case for Heathrow needs more careful consideration.
Heathrow was the frontrunner but now Gatwick is back in the race. Gatwick has less of a pollution problem and fewer local residents to upset but it too will face fierce opposition.
There are plenty of campaigners who are determined that we need to start prioritising the environment over economic growth.