Here's why it was halted - like a few others mentioned.IIROC Trading Halt - AC.B
5 minutes ago by CNW Group
The following issues have been halted by IIROC:
Company: Air Canada
TSX Symbol: AC.B
Reason: Single-Stock Circuit Breaker
Halt Time (ET): 11:01:46
The Investment Industry Regulatory Organization of Canada (IIROC) can make a decision to impose a temporary suspension of trading in a security of a publicly listed company, usually in anticipation of a material news announcement by the company. Trading halts are issued based on the principle that all investors should have the same timely access to important company information. IIROC is the national self-regulatory organization which oversees all investment dealers and trading activity on debt and equity marketplaces in Canada.