WestJet Airlines Ltd's (WJA.TO) joint venture with Delta Air Lines Inc (DAL.N) will put the Canadian air carrier in a stronger position to gain market share, credit rating agency Moody's Investors Service said.

WestJet on Wednesday announced the Delta joint venture to boost its trans-border flight service and said it expects to nearly double the number of aircraft owned by the carrier by 2020 as it targets both cost-conscious passengers and higher-paying customers.

WestJet's decision is credit positive for unsecured debt holders. However, it faces execution risk in carrying out large scale projects simultaneously, Moody's said in a note published on Thursday.

Shares of Canada's second-largest air carrier were up 0.8 per cent on Friday.