The bosses of London's four major airports are to give evidence to the Transport Select Committee, as it investigates the Government's aviation policy.
Colin Matthews, chief executive of Heathrow; Stewart Wingate, chief executive of Gatwick; Glyn Jones, managing director of Luton and Nick Barton, managing director of Stansted are due to be questioned this afternoon.
Campaigners opposed to airport expansion are also due to appear. Tim Johnson, director of Aviation Environment Federation and Chris Crean from Friends of the Earth are two of the organisations who'll face MPs questions.
More top news
Official readings are recorded three metres in the air but a study found levels of nitrogen dioxide (NO2) were higher at pushchair level.
Tubes, trains, trams, buses, cable cars, river buses, taxis and going by foot - your guide to getting around during the strike.
Union officials rejected a revised offer from Underground managers during a meeting at the conciliation service ACAS this afternoon.