When we first got the 300's, they were a maintenance nightmare (and still are, but they're FINALLY starting to catch up). When one would break, they would toss a 200 on the line. They also committed to the flying before they had the airplanes ready to go, and there was about 2 months where we had airplanes that weren't ready and pilots/flight attendants who weren't trained to fly them. It was like 20 lines of flying with 16 airplanes. That ain't easy to do...