WestJet Airlines has requested permission to contribute to a Competition Bureau investigation into a joint venture between Air Canada and United Continental Holdings.

The Canadian low-cost carrier argues the deal could hurt its ability to compete on flights to the United States.

“WestJet is of the view that if the relief sought by the commissioner is not granted, WestJet’s ability to enter and/or expand its transborder air passenger services on the transborder overlap routes will continue to be significantly prevented or lessened,” the company’s executive vice-president of strategy and planning, Hugh Dunleavy, said in an affidavit seeking intervener status in the case.

Air Canada wants to expand on its existing alliance with United Airlines and Continental Airlines to co-ordinate on sales, fares, schedules and marketing on 19 routes between Canada and the United States.

The deal would also see the airlines – both members of Star Alliance - pool resources and revenue share.

Competition commissioner Melanie Aitken has applied to the competition tribunal to stop the deal.

She argues the deal amounts to a merger which could lead to higher fares.

As many as ten of the 19 routes planned for cooperation would become monopolies, argued Ms Aitken.