A new runway will be needed in south east England in the coming decades, the head of the Government-appointed Airports Commission said today.
The options to meet demand could include expansion at Stansted or Luton airports.
Sir Howard Davies said pressure on the UK's busiest airports was likely to continue to grow.
Speaking in London today, Sir Howard said: "Our provisional conclusion is that we will need some net additional runway capacity in the south east of England in the coming decades."
The commission is due to make an interim report before the end of the year, when it will make short-term recommendations involving making more use of existing aviation infrastructure.
A final, full report, making recommendations for the long term, is due after the May 2015 general election.
Sir Howard, a former CBI chief and a former head of the Financial Services Association, said: "Our final conclusions will certainly not please everyone. I am sure about that."
Labour had approved an extra, third runway at Heathrow airport, but this plan was scrapped by the coalition Government when it took power in May 2010.
Since then, the Heathrow plan has gained more supporters, while London Mayor Boris Johnson favours a new, Thames Estuary airport or expansion at Stansted, while there has also been backing for another runway at Gatwick in West Sussex.
Other arguments have included the expansion of regional airports.
Sir Howard said he hoped the commission would be able to put forward one main option when the final report is made in 2015, although he admitted that no one single option could cover absolutely every contingency.