To ask the Secretary of State for Transport how many flight hours were expended by commercial aircraft in 2007-08 in stacking while awaiting clearance to land at Heathrow; and how much carbon dioxide was emitted by those aircraft while stacked. (254720)

The Department for Transport's report, ‘Improving the Air Passenger Experience’, provides appropriate estimates of aircraft stacking above Heathrow in Figure 27 on page 25. This report is available at:

http://www.dft.gov.uk/pgr/aviation/airports/improve airpassenqer.pdf

Data for 2007-08 are not available. However, in 2006-07, aircraft were held in aggregate for 18,679 hours. This is based on 56 per cent. of arriving aircraft being held in a stack and an average 8.5 minute hold for those held. This equates to roughly 50,000 tonnes of carbon dioxide emitted by aircraft stacking at Heathrow.