New proposals from the avation regulator mean airlines will be charged less for using Heathrow, Gatwick and Stansted - limiting potential fare hikes for travellers.
The three airports are the only ones regulated by the Civil Aviation Authority (CAA), which can cap the amount the airports can impose on airlines in take-off and landing fees.
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Paramedics were on standby outside the police cordon as armed officers stood by the property.
A team of researchers has taken samples from the ten busiest London Underground lines to work out which are the dirtiest.
The action comes on top of an emergency timetable which has seen hundreds of trains a day being axed.