A merger would reportedly create the second biggest airline in the US

Two of the biggest airlines in the United States - United and US Airways - are discussing a possible merger, reports say.

The companies are said to have spent two weeks deep in talks but have not yet reached a deal.

There have been a number of tie-ups between prominent airlines since their industry was hit by sharply higher fuel prices and the global recession.

Spokesmen for both companies said they would not comment on the speculation.

Reports of the talks in the New York Times and Washington Post newspapers prompted stocks in both airlines to rise in after-hours trading on Wednesday.

US Airways shares leapt by $1.35 - or 20% - to $8.17, while United's parent company UAL Corporation rose $1.53 (8%) to $20.48.

A merger between the two companies would create America's second-biggest airline after Delta Air Lines, reports say.

The International Air Transport Association said the global airline industry sector would make a combined loss of $2.8bn (£1.9bn) this year, with European and US airlines suffering the most.