Officials at the UC Davis Medical Center, where Stone is currently being treated, said today his condition was upgraded from serious to fair.
"He is awake, able to get out of bed and in good spirits. He is continuing to recover," the hospital said in a statement.
Stone underwent surgery Thursday after suffering three stab wounds to the torso, officials said. Dr. J. Douglas Kirk, the medical director at UCDMC, said Thursday that Stone was expected to make a full recovery.
Stone, 23, was "involved in a stabbing incident" in Sacramento, California, early Thursday morning, according to an Air Force spokesperson.
The Sacramento Police said "it is believed that Stone was out with a group of friends when a physical altercation led to him being stabbed multiple times in his upper body. Immediately after the assault the assailants fled the scene."
"We firmly believe that this is not a terrorism related event and that it is in no way related to the incident that occurred in France," the police said.
"The assault does not appear to be a random act and is believed to be a nightlife related incident," the police added, noting the incident is under investigation by local law enforcement.
This summer, Stone was traveling on board a train heading to Paris with two friends when the train came under attack by a gunman. Stone and his friends confronted the gunman, helping stop the attack.
Stone had surgery to reattach his thumb after it was cut off with a box cutter by the train attacker.