WestJet and Delta Air Lines have agreed to deepen their partnership with a preliminary agreement to form a joint venture.

Both airlines said in a statement early Wednesday that the agreement will increase travel choices between Canada and the United States along with enhanced frequent flyer benefits.

Calgary-based WestJet and Delta said the agreement includes co-ordinated schedules for new non-stop flights to new destinations and expanded codesharing.

The airlines said the planned joint venture is subject to board and regulatory approvals in both the U.S. and Canada.

"This agreement will bring heightened competition and an enriched product offering to the transborder segment," said WestJet executive vice-president Ed Sims.

"This is an important step in WestJet's mission to become a global airline."