Upslope, Valley and Radiation - there are many names for fog. Here's why they're different.
12 weeks from now the first flights will be arriving at the new terminal, which will cater for 20 million passengers a year.
The investment is likely to reinforce Heathrow's case for runways and weaken the argument for a new hub airport in the Thames estuary.
Bosses from Heathrow, Gatwick and Stansted will gather at a forum in Westminster later today to discuss options for the future of London's airports.
Heathrow CEO Colin Matthews is one of several high profile speakers, including Gatwick CEO Stewart Wingate and Stansted managing director Andrew Harrison.
Discussion will centre around possible long term proposals put forward to improve the UK's airport capacity - including the construction of a third runway at Heathrow, the possibility of a hub airport in East London and the expansion of Gatwick and Stansted airports.
Weapons including stun guns and flick knives have been found in luggage at Heathrow airport.
Border Force officers were carrying out checks in Terminal 3 and uncovered three stun guns, a throwing star, two knuckledusters, an extendable baton, a pair of nun-chucks and two flick knives. A 57-year-old man from Swansea, who had just arrived on a flight from Bangkok in Thailand, was arrested.
Marc Owen, Border Force Heathrow Director, said:
"In the wrong hands these items could be potentially lethal, which is why the controls on bringing them into the UK are so strict. Although items like stun guns and knives are more readily available in some countries we urge people to think twice before attempting to bring them back into the UK."
Two women have been arrested on suspicion of terror offences in separate police swoops, with one of them stopped at Heathrow Airport as she tried to board a flight to Istanbul, Turkey.
The woman, aged 26, was arrested on suspicion of being involved in the commission, preparation and instigation of acts of terrorism after trying to board the flight at 9.20am in Terminal 5. A "large quantity" of money was seized.
The second woman, aged 27, was arrested five hours later in north-west London on suspicion of the same offences.
Scotland Yard said the arrests were intelligence-led rather than in response to an immediate risk or threat and both women are being questioned.
Two addresses in north and north-west London are also being searched.
Two women aged 26 and 27 have been arrested on suspicion of being involved in the commission, preparation and instigation of acts of terrorism, Scotland Yard said.
Speaking at the aviation conference in London today, Mr Johnson's aviation adviser Daniel Moylan said Mr Johnson had not been consulted about the setting up of the commission and had been "profoundly unsettled" by its interim report.
– Daniel Moylan, Mayor's aviation adviser
Heathrow expansion is not any answer at all, for the proven political reason that it is too toxic for any Government to deliver.
To delete the option of a new airport from the process would mean there was only one solution left that satisfied the Commission's remit: a new runway at Heathrow followed by a fourth.
That is not a bargaining position that any Government will accept or a prescription that any Government will deliver.
Speaking to ITV News London, David Cameron said he had "great faith" in the Head of the Airports Commission, Sir Howard Davies. The Prime Minister added that "all options were still on the table", including an airport east of London.
Watch the interview with David Cameron in full on ITV News London at 6pm.
Martin Lomas, Deputy Chief Inspector of Prisons said Mr Dvorzac had been in handcuffs for almost five hours and was still wearing them when he died:
The use of restraints in this case was shocking. All senses of humanity seem to have been lost.
Clearly the performance by the contractor running Harmondsworth has been below the high standard expected. It is for the Home Office to decide if the contact should be removed.
Harmondsworth now needs to concentrate on the needs of the most vulnerable men it holds at the centre.
At today's conference Sir Howard Davies said that with the estuary option there was the "simple challenge of distance", with the schemes being some way from central London. He added:
The economic implications are quite serious as well, such as what would be the effect of closing Heathrow and London City airports.