Bushman
Some airlines had manufacturer's warranties that rewarded the customer for using a "smaller" engine for takeoff for a certain number of years. The more you could safely use TO1 or TO2, the happier the manufacturer was, and the better "deal" on coverage. The TO, TO1 and TO2 settings essentially provided 3 different certificated engines: big, medium and small.....as they were "fixed" derates. Each one was considered "max" for that "size" of engine. The AT derates provided even further cuts....up to 40% total from TO. On a fully AT-derated TO2 takeoff (obviously light weight with friendly runway/obstacles), we called them "Idle Power Takeoffs."