As thousands of air passengers in Canada and around the world scrambled to adjust travel plans ahead of a potential strike by Air Canada’s flight attendants, the country’s labor minister asked the workers’ union if it was open to government arbitration to avert a walkout.

Patty Hajdu, the minister, gave the union until noon Eastern time on Friday to respond to a request from Air Canada to settle the labor dispute through binding arbitration. Government-mandated arbitration is normally used to end long and disruptive walkouts, not to block a strike before it begins.

Hugh Pouliot, a spokesman for the Canadian Union of Public Employees, of which Air Canada’s flight attendants are members, said it would reject arbitration.

“We will not surrender our constitutionally protected right to strike,” he said.

Ms. Hajdu did not indicate what she would do if the union rejected the airline’s latest attempt at arbitration. She has continually urged the two sides to resume direct negotiations, which broke down over wages and the union’s demand that the company pay attendants for the hours worked before planes take off and after flights land, known as groundwork.

Arbitrators rarely introduce major new changes — like groundwork compensation — in contracts they impose.

Air Canada began canceling flights on Thursday, after the union issued a notice that it intended to strike at 12:01 a.m. on Saturday. The airline responded with a similar notice, saying that it planned to lock out the flight attendants at the same time.