Longview Communications & Public Affairs is guiding Onex Partners' $3.5B acquisition of Calgary-based Westjet, a deal that marks the largest-ever private equity takeover of an airline.

The $31 per-share offer represents a 67 percent premium over the May 10 closing price of Westjet's shares on the Toronto Stock Exchange.

It marks Onex's third bid for an airline, following its failed runs at Air Canada and Australia's Qantas Airways.

Launched by Clive Beddoe in 1996, Westjet flies to more than 100 destinations in North America, Central America, the Caribbean and Europe. It has more than 14K employees.

“WestJet is one of Canada’s strongest brands," said Tawfiq Popatia, managing director at Onex, adding the carrier is noted for its" unparalleled guest experience and employee culture."

Canada 's Minister of Transport must approval the Onex deal. That is expected early next year.

Longview's Martin Cej represents Onex in the transaction.

The firm bills itself as Canada's leading independent corporate communications and PA shop. It has offices in Toronto, Ottawa, Winnipeg, Calgary and Vancouver.