Airbus entered the debate over airport expansion by warning that more runways are needed to accommodate a doubling of the global aircraft fleet by 2026.

The European plane maker predicted that 28,534 passenger and freight aircraft would be flying in less than two decades' time - more than double the current total of 13,284.
Britain will be the third largest customer for new aircraft, Airbus said, with 1,100 jets to be added to aviation infrastructure that is already under severe strain. Heathrow, Gatwick and Stansted, Britain's largest airports, operate at near capacity and the government is consulting over proposals to build a third runway at Heathrow by 2020.
Airbus refused to be drawn on the proposed expansion at Britain's biggest flight hub but admitted more runways would be needed to meet its forecasts.
Laurent Rouad, a research executive at Airbus, said: ""There is a physical limit. We need more capacity in airports, higher capacity airplanes and greater frequency of flights. And then we need to balance all three.""
Ruth Kelly, transport secretary, has warned that failure to expand Heathrow would damage the economy and would have no impact on global warming because the air traffic would simply move to continental Europe.
Global forecasts
The Airbus global forecast adds 1,600 aircraft to the previous 20-year estimate, despite fears that the softening US economy and high oil prices will hurt demand for air travel over the next year. The company, based in Toulouse, said soaring fuel costs had caused the upwards revision because airlines would accelerate replacement of older aircraft, which consume expensive fuel more voraciously than newer models.
Airbus moved to head off the inevitable green backlash against its latest predictions by stating that nine out of 10 planes now flying would be decommissioned by 2026. The replacement jets will include 1,700 aircraft of a similar scale to the company's A380 superjet, which carries hundreds more passengers and burns 20% less fuel than its predecessors. However, the company said aviation's contribution to global carbon dioxide emissions would grow from 2% to 3% over the period - a figure disputed by environmental groups, which say it will be even higher.
Tim Johnson, director of the Aviation Environment Federation, said fuel consumption targets - such as the 50% reduction by 2050 suggested by some Boeing executives - must be brought forward by several decades.
""Even allowing for the incremental efficiency gains that new aircraft are going to bring the global fleet, we are still talking about a near-doubling of carbon-dioxide emissions by 2026. Therefore, the targets that manufacturers are setting need to be radically different,"" he said.
Airbus and Boeing, which are neck-and-neck in the aircraft manufacturing race, argue that producing a significant change in aviation technology within a decade is financially and logistically impossible.
For instance, Boeing is hoping that the next generation of aircraft after its new 787 Dreamliner, which has yet to enter commercial service, will produce 15% less carbon dioxide than its latest highly fuel-efficient model but those jets will not enter production until 2015 at the earliest.
Airbus also raised the prospect of aircraft being powered by alternative fuels by 2026. The debate over the environmental merits of biofuels has become increasingly heated, while there are doubts over the ability of biofuel producers to meet the aviation industry's needs.
According to one estimate, if the entire land mass of Florida was given over to producing plants for use in biofuels, the end result would cover the annual fuel needs of just 10% of the U.S. domestic aviation industry. National Express, the rail and coach group, has pulled out of a biofuel trial amid fears that it was doing more harm than good to the environment.
Demand takes off
The biggest demand for aircraft in the next 20 years, Airbus says, will come from the U.S. and China. U.S. airlines, emerging from a post-9/11 slump, will spend $500bn (£250bn) on 5,800 new planes and China will order 3,000 more by 2026. Low-cost airlines will acquire about a third of the aircraft bought worldwide, it said, with flag carriers such as British Airways and Australia's Qantas buying the rest. The 550-seat Airbus A380 looms large over the industry but Airbus expects the biggest seller to be the single-aisle jets used on short-haul routes.