The majority of WestJet's nearly 1,300 pilots have voted against forming a union at the Calgary-based airline, according to the WestJet Professional Pilots Association.

The decision comes after a nearly two-year campaign and two weeks of secret ballot voting.

In a release on its Facebook page, the association said that 1,247 pilots voted — 561 voted Yes, while 684 voted No, with two spoiled ballots, resulting in 55 per cent of pilots voting against certification.

The pilots association said it was disappointed with the result.

"We hope the open discussions that have taken place as part of this process will set the stage for constructive dialogue between our pilots and WestJet leadership going forward," the group said in the release.

The Canada Industrial Relations Board (CIRB) said it will examine the results before they are considered official.

"We are pleased that the majority of our pilots who voted have voted against union representation," said WestJet chief executive Gregg Saretsky in a statement. "Despite the positive outcome, there is continued work that needs to take place to better understand some of the issues for our pilot group and we can now turn our efforts to that goal."

The airline fought the union drive in public and behind the scenes. According to documents obtained by CBC News, WestJet challenged the validity of the pilots' vote and the legitimacy of the signed union cards. But the CIRB ruled the vote could go ahead.

Airline executives spoke out against the union, warning about repercussions.

WestJet's chief executive Gregg Saretsky had sent an email to all of WestJet's staff, urging them to think twice before signing a union card. "Having a union as your exclusive bargaining agent would have a significant impact on the nature of your employment and the way the company and employees interact with each other," said Saretsky in the email to employees in June.

In a document attached to the email, WestJet said that a union cannot guarantee anything, including the terms of employment, current wages and profit sharing and the employee share purchase plan.

Clive Beddoe, the co-founder and current chairman of the airline, also wrote to employees, strongly disagreeing with the need for a union. He said WestJet's success hinged on its "unity of purpose" and co-operation instead of confrontation.

Both pilots and flight attendants have tried to unionize. The pilots are looking for more transparency on upgrading from first officer to captain, as well as more equality with their colleagues who fly for WestJet's regional airline, Encore.

The demands of the flight attendants group include seeking more input into their work rules.

Both groups are looking for a more formal relationship with management at an airline that has grown rapidly over the past several years, launching Encore, expanding its crew bases to Vancouver and Toronto and adding wide-bodied jets to fly to Europe.