The investment comes at a shaky moment for travel between Canada and the U.S., with Canadians taking fewer trips to the U.S.

Delta Air Lines and Korean Air will take equity stakes of a combined 25% in WestJet, worth $550 million. Delta will take 15% and KAL 10%. After the deal closes, Delta plans to transfer and sell a 2.3% stake to its joint venture partner Air France-KLM, which also has an existing partnership with WestJet.

Delta Air Lines and Korean Air Lines will acquire an aggregate 25% stake in Canada's WestJet Airlines for $550 million from private equity firm Onex Corp, the U.S. carrier said on Friday. Delta will invest $330 million for a 15% stake and Korean Air will inject $220 million for a 10% interest.