Air Canada shares sank 22 percent on Tuesday as analysts speculated the resignation of its chief executive, and the naming of a replacement known for his restructuring expertise, may signal its second filing for creditor protection in six years.

Montie Brewer, who has led the airline through the industry downturn and has had to scramble to raise cash while competing with rival WestJet Airlines, will be replaced on Wednesday by Calin Rovinescu, a key figure in Air Canada's last corporate revamp under bankruptcy protection.

Air Canada's class B shares fell 25 Canadian cents to 90 cents on the Toronto Stock Exchange. Its A shares fell 18 Canadian cents to 90 cents.

Rovinescu is a lawyer who was Air Canada's vice-president of corporate development and strategy from 2000 to 2004, a period that included the airline's last restructuring and emergence from creditor protection.

He subsequently co-founded Genuity Capital Markets, a Canadian investment bank.

Analyst Jacques Kavafian said his appointment as Air Canada CEO signals another restructuring because of his legal experience and his unpopularity with the carrier's unions.

"In fact, we believe that his resignation from Air Canada in 2004 was a condition for union acceptance of wage concessions," Kavafian said in a note to clients. "Bringing him on just as new labour agreements are to be negotiated does not square with the unions' historical sentiments."

Kavafian also took note that Rovinescu will take up his post six years to the day after Air Canada last filed for creditor protection.

"While the challenges in front of us are large, we will continue to build upon the successes of the airline to date and deliver a quality product for our customers, employees and shareholders," Rovinescu said in a statement.

Airline spokeswoman Angela Mah declined to comment on what might be in the cards for Air Canada beyond what was in the statement, issued late on Monday.

It made no mention of plans to seek creditor protection.

However, Chief Operating Officer Bill Bredt announced on Tuesday he too is retiring, and will be replaced by Duncan Dee.

Air Canada shares have tumbled over the past year as the airline industry downturn that first took hold in the United States spilled into Canada.

The carrier cut its capacity by 7 percent, which meant 2,000 layoffs, and has been working to raise capital to shore up its balance sheet.

It also faces a pension deficit and brisk competition on fares and routes from Calgary-based WestJet.

"Suddenly and dramatically, bringing in someone like Mr. Rovinescu... speaks to the extreme turmoil currently taking place at Air Canada," Ben Cherniavsky, an analyst at Raymond James, wrote in a research note.

Cherniavsky has pegged the changes of Air Canada's survival at "50/50, at best."