MONTREAL - The largest private-sector union in the country says Air Canada is employees' best option when it comes to the purchase of Quebec tour operator Transat A.T.

Unifor president Jerry Dias argues in an open letter that while takeovers can work against employees' best interest, his union is backing the option that offers the most stability.

Last month Transat's board of directors approved a takeover offer by Air Canada over other bidders, though the $520-million deal faces legal and regulatory scrutiny along with resistance from major Transat shareholders.

The announcement came three days after Ottawa greenlighted Onex Corp.'s proposed $3.5-billion acquisition of WestJet Airlines Ltd. on June 24.

Dias said in a phone interview Wednesday that hedge funds have little stake in protecting companies in the long-term and frequently wind up selling off profitable parts before abandoning ship.

Unifor represents more than 4,000 sales and customer service agents at Air Canada, but no employees at Transat, where about half of the 5,000 workers are unionized.