The deadline to finalize an 'open skies' pact between the U.S. and EU has been pushed back to next March after negotiators failed again to work out details to liberalize the trans-Atlantic aviation market.

One of the biggest sticking points is reluctance on the part of Congress to allow foreign investors greater control over U.S. air carriers.

Nonetheless, a U.S. transportation official said, “By the end of the year, we would hope to have a signed, sealed and delivered agreement.''

Negotiators have been working on an open skies agreement between the U.S. and EU for a decade.