Yesterday, I flew from Portland, OR to Philadelphia via Chicago on American Airlines. In the past, they boarded passengers starting at the back and working forward. Yesterday, they boarded in "groups". I was in group 4 and seated near the back of the airplane, yet group 4 was the last to board. It's been a couple of months since I've flown on a commercial airline and I'm curious about what's going on here - is this a new security procedure?