After going for an incredibly long stretch without experiencing any delays on AC due to mechanical problems I have had 4 in the last 3 weeks all exceeding two hours and all involving Embraer planes. The most recent was AC 464 yesterday. I have no idea what the problems have been. In 3 of the cases we were moved to a different plane such as with AC 124 on March 25th. Just bad luck or is something going on with these planes?