Labour Minister Lisa Raitt says she will refer the two failed attempts between Air Canada and its flight attendants to reach a deal to the Canada Industrial Relations Board, which prohibits a possible strike until the agency issues a ruling on the case.

Raitt told CTV's Power Play Tuesday that she intends to refer the issue to the CIRB on Wednesday, and while the agency is probing the matter, "there cannot be a work stoppage."

"It's not only about the work stoppage and the notice of the strike, but it's the overall way in which the ratification failed," Raitt said of why she wants the CIRB to examine the matter.

Raitt said while the board could render "a quick decision," it can take all the time it needs to interview all the parties to find out how the Canadian Union of Public Employees reached two agreements with the airline that flight attendants then failed to ratify.

She also said that as a back-up plan, the government does have a notice on the order paper of its intent to introduce back-to-work legislation if flight attendants eventually do strike.

On Sunday, CUPE announced that nearly two-thirds of the flight attendants who took part in a Sunday vote did not support the deal that had been negotiated with Air Canada.

That has put the flight attendants in a legal position to strike at 12:01 a.m. Thursday.

Air Canada has said it is preparing for the likely possibility that its 6,800 flight attendants could be headed off the job.

Duncan Dee, the chief operating officer of Air Canada, said the airline is "perplexed" as to why its flight attendants rejected back-to-back deals.

"We are perplexed and disappointed that two tentative agreements negotiated in good faith with and unanimously recommended by the democratically elected representatives of our flight attendants have failed to be ratified," Dee said in a statement posted to the Air Canada website earlier Tuesday.

"Air Canada remains hopeful that a disruption can be avoided."

In any case, the airline says it intends to offer a partial schedule should a strike ensue.

The flight attendants rejected a prior tentative agreement in August, which sent union negotiators into a new set of talks with Air Canada that produced the deal that was turned down Sunday.

Airline analyst Karl Moore told CTV's Canada AM that there are some flight attendants who are now calling for heads to roll, after union representatives offered members two unsatisfactory deals in a row.

"The members just don't feel this is what they want to get out of Air Canada and so voted it (the latest deal) down, and a number of members have gone to set up a petition to oust some of the union officials," Moore said Tuesday morning.

"So there's some differences between the officials and the rank and file members of the union."

Some of the key issues in the dispute between the flight attendants and the airline include wages, pensions, crew rest, working conditions and work rules.

Raitt said Tuesday she was told by union officials that they had received 80 per cent of what they asked for, so it is unclear "what the difficulty is."

"In this case, we've got a situation where two times you've had unanimous recommendation of a deal and two times ratification has failed," Raitt said. "We want to know why, what happened, and we want the parties to talk about what their process was, and maybe there's something that happened within the ratification vote that the CIRB can take a look at."

Moore said it is rare for Ottawa to force union members back to work, but like in the recent postal strike, it is the government's view that an Air Canada work stoppage would harm the economy.

"The argument they are making is that Canada Post, and in this case Air Canada, are so important to our economy that we can't afford to have them out," said Moore.

With files from The Canadian Press