London Heathrow operator BAA will be directed to ensure that "green slots" are used efficiently as the UK government looks to mitigate the environmental impact of the proposed third runway.
Green slots will be available to carriers with the newest, cleanest aircraft when the planned runway and sixth terminal become operational, which is targeted for between 2015 and 2020.
Speaking at the International Aviation Club in Washington DC this week, UK transport minister Geoff Hoon said that a duty will be placed on the airport's operator BAA to ensure that airlines - new entrants in particular - do not change the carbon footprint by using green slots for older, higher polluting aircraft.
Towards the end of this year the government will begin discussing how to allocate green slots and how many slots will be designated as green. Industry input will also be sought.