When the Airports Commission recommended a new runway at Heathrow Airport last July, something very rare occurred. In October, mayoral candidates Zac Goldsmith, Sadiq Khan, Caroline Pidgeon and Sian Berry all addressed a crowd at the No Third Runway demonstration, putting differences aside for one afternoon to denounce the commission's decision.
While united on this front, the question of airport expansion goes deeper, especially when you factor in the announcement from the UK Government that a decision on whether to build a third runway at Heathrow has been delayed until at least this summer.
'I'll call by-election if Heathrow gets green light'
Zac Goldsmith, the Conservative candidate and MP for Richmond, generated headlines when he announced that he would trigger a by-election in his Richmond seat if Heathrow expansion gets the go-ahead. He has been steadfast in his opposition for many years, but did confirm that if elected mayor he would not resign in the event of a third runway being built.
The government's decision to delay has been a welcome boost for him, and in bullish mood he declared in December that Heathrow was "off the radar". It is not that cut and dry yet, but his persistent warnings on the environmental impact have been a thorn in the side of Heathrow bosses. He even claimed in January that the airport could not pass air pollution tests.
He said: "If [it] passes the air pollution test and is given a green light, that could only mean that the test has been set in such a way that Heathrow was always going to pass it." But, what of his views on expansion at Gatwick?
This is where the cracks between the candidates begin to show. Labour's Sadiq Khan is in favour of expanding Gatwick, as well as developing what is being called Heathwick; a fast rail link between the two airports. He has even gone as far as to suggest Labour should adopt this as official party policy. However, he has been attacked for a change of heart, after previously voicing support for Heathrow when part of the last Labour government.
In an interview with the London Evening Standard, he told how his main rival, Goldsmith, is "against any expansion at all. No expansion is damaging for London". What Goldsmith has championed is greater competition, arguing that Heathrow as a hub airport is not the answer. He believes such a move could create a monopoly and choke the life out of competition and choice.
Khan also follows a similar line, declaring "competition between two primary airports" is better for all the economy and passengers. Those who advocate increasing hub capacity claim it is vital to ensure the UK competes with international rivals.
While not explicitly expressing his support for Gatwick, Goldsmith said towards the end of last year: "If and when there is need for additional capacity ... it would need to be at either Stansted or Gatwick, whichever can offer the best value for money without compromising carbon, noise and air-quality limits." Again, no chance to express his 'green' agenda is missed.
No to any expansion
The Green Party's Sian Berry has gone one step further, opposing all airport expansion. Her view is that it is unnecessary and will only compound the growing problem of air pollution in the city - building a new runway at either Gatwick or Heathrow will "make it impossible to meet our climate targets", she said.
Berry also has a radical plan to close down and redevelop London City Airport into a homes and business area - (note, Mayor Boris Johnson has just rejected a £220m bid to expand the airport). Her reasoning being that the airport is damaging the environment and lives of nearby residents. The Green candidate also says it is "holding back London's economic potential".
A report by the New Economics Foundation gives some weight to this, predicting that the site could be used to create 16,000 jobs and add £400m to the economy. City Airport unsurprisingly hit back, calling Berry's views "ill-informed".
Polling suggests that Berry is unlikely to be elected, but her ideas have struck a chord with those who are fed up of arguments of economic growth continuously taking priority over environmental concerns. Stopping all expansion also removes the prospect of what Berry has termed the 'pushing of problems on to other residents'.
For the Liberal Democrats, Caroline Pidgeon - "we need to clean up our air not make it worse" - joins her other candidates in the anti-Heathrow lobby and, like the Greens, says no to any expansion in London and the South East. "I don't believe the aviation industry and their demands," she added in February. "I think there's a lot of rumour and counter rumour in this industry."
Rather, Pidgeon argues that existing capacity can be used more effectively and agrees with Goldsmith that a hub airport is not essential. She also wants to improve rail links to cut down on the number of short-haul flights.
A seldom observed consensus has emerged in the mayoral race: no to Heathrow.