Arch rivals British Airways and Virgin Atlantic are to join forces to tell MPs of their opposition to a so-called "open skies" EU-US deal.
The draft aviation agreement, to be discussed by EU transport ministers next week, is designed to give UK airlines more freedom to fly to the US and allow American carriers more rights to travel to the UK and Europe.
But both BA and Virgin argue that the deal does not give UK airlines the same rights to fly within America as US carriers will have to fly within Europe.
The two airlines will appear before the House of Commons transport committee.
Another UK airline, bmi, will give evidence, as will Transport Secretary Douglas Alexander, who has already expressed some reservations about the new deal.
Under the long-standing existing transatlantic air agreement, BA and Virgin, as well as US carriers American Airlines and United, are the only airlines able to fly to America from Heathrow Airport.
Years of talks between the UK, the EU and America had failed to come up with a fresh agreement until this latest recommended draft agreement.
However, BA believes the deal is no better for the UK and the EU than ones already rejected by the EU earlier this decade.
Supporters of the new agreement believe transatlantic fares will come down and that BA and Virgin are only voicing objections as they want to preserve their "protected" positions at Heathrow.
Last week, Mr Alexander said there is still work to do on the deal and that the proposed agreement fell short of providing the kind of access to the US market that a number of EU carriers would like.
