Originally Posted by
Clandestino
What NTSB has written about STS being installed on NGs is true but it's not the whole truth: STS has been introduced on 737-300.
More of a half truth. The FAA certified the 737NG without STS, however JAA would not certify the aircraft as it did not meet certification standards. To meet the JAA certification standards Boeing were forced to install STS, that was subsequently retrofitted to all 737NGs as standard.