Accident investigators looking into the 737 Max crashes have implicated a key system known as MCAS. Now it appears that a version of the system Boeing created years earlier for a military fuel tanker had a better design.

That’s according to a Wall Street Journal report published today on the system’s history and the push to build safeguards into it for the tanker, known as the KC-46A Pegasus. It’s a plane based off Boeing’s 767 passenger jet. Those safeguards were not incorporated into the version installed on the 737 Max. On both planes, the system is intended to combat the natural tendency of the airplane to pitch upwards.

Notably, pilots of the KC-46 are able to override the MCAS—or Maneuvering Characteristics Augmentation System—simply by pulling on the controls, the Journal reports. It quotes an Air Force procurement chief as saying, “We have better sensor data. But most importantly, when the pilot grabs the stick, the pilot is completely in control.”