Keep in mind that American's AAdvantage program does not allow stopovers on award tickets, but you can book one - way awards. (upgradedpoints.com)
You can also book stopovers on award tickets with Singapore Airlines. (upgradedpoints.com)
All three of the major U.S. airlines — American, United and Delta — used to allow free stopovers on award tickets, but that's not the case anymore. (rewardexpert.com)