THE world’s airlines are expected to say this week that Heathrow is finally full up. The airport is set to reach its maximum number of permitted flights next summer.

The statement, by IATA, the world airline trade body, will come just days ahead of an expected announcement by the government of plans for a third runway at Heathrow.

Whitehall sources said Ruth Kelly, the transport secretary, is likely to unveil a consultation document on the extra runway on Friday.

Heathrow is limited to 480,000 flights a year. The limit was agreed as part of a series of planning decisions that approved the construction of new terminals.

It is running close to that limit.

In the airline “winter” season, running from October to March, it is operating at a rate equivalent to 477,000 flights a year.

Last week international airlines met in Toronto to trade runway slots. Services negotiated for Heathrow for the next summer season – April to September 2008 – will see it reach the 480,000 threshold for the first time.

IATA has long urged airport companies and governments to tackle infrastructure bottlenecks at airports, and this week’s statement will be seen as an attempt to influence the debate over expansion at Heathrow.

Kelly is expected to unveil a two-stage expansion in flights. First, the government proposes changing the way the airport’s runways are operating, which will allow an increase to about 550,000 flights a year.

The changed operations will mean more overflights for London residents, and are likely to draw considerable opposition from environmentalists and local councils.

The second phase will involve the construction of a third runway, and a new, sixth, terminal, to the north of the two current strips.

If fully utilised, the extra runway could see flight numbers jump to 720,000 a year. Kelly will say that the runway could not open before 2015 at the earliest. She is also likely to reveal a carbon-offset plan to limit environmental damage.

Attempts to expand Heathrow have always been fraught with difficulty. Its new fifth terminal, which will open in March, took 20 years to build, including four years taken up with a planning inquiry.

In 2003, a government white paper on aviation policy backed new runways at Stansted and Heathrow, but said the latter could not proceed until local air quality improved.

Times Recommends

• Minister in talks with Saudis to protect creditors
• Premier Inn hits back in £29-a-room row
• Bankers hit back at 'populist' bonus supertax