Tucson, Arizona (CNN) -- U.S. Rep. Gabrielle Giffords on Thursday continued her dramatic recovery from a gunshot wound to the brain by going outside for physical therapy, one of her principal doctors in Tucson, Arizona, told CNN.
"Today actually, we were glad to say that we were able to take her outside and she was able to do her physical therapy," Dr. Peter Rhee told John King.
"We gave her some fresh air and also gave her some sunshine," said Rhee, speaking from outside University Medical Center. "She was able to see the Arizona mountains."
Behind Rhee, flowers left by well-wishers filled a portion of the hospital lawn.
A day before she was to be flown to a Texas hospital, the husband of Giffords, shot in the head less than two weeks ago at a public event, described his wife's progress as "remarkable."
Mark Kelly said Thursday he is hopeful the Arizona congresswoman will make a full recovery.
"I've told her that," Kelly told reporters at University Medical Center. "She recognizes it ... she is a fighter like nobody else that I know."
Giffords is able to stand with assistance, but is not yet able to take steps or walk, said Rhee, adding therapists are helping Giffords with ways to express her thoughts and, eventually, speak.
"[We are] holding her up so she can train herself to hold her head up," Rhee said. "She is learning to balance and learning all the little things we can take for granted."
Giffords, 40, was shot in an assassination attempt and mass shooting that killed six and wounded 13 at a Safeway grocery store in Tucson on January 8. The congresswoman is the only person still hospitalized after the attack, the hospital has said.
Giffords will be taken by ambulance Friday morning from University Medical Center in Tucson to Davis-Monthan Air Force Base. Giffords will be flown to Houston, where she will receive further treatment at Memorial Hermann-Texas Medical Center, her office said in a statement.
On Wednesday, the public learned that Giffords was able to rise from her hospital bed and stand with assistance.
Kelly said that while what physical therapists classify as "standing" or "steps" and the clinical definition of it are "a little bit different," he said his wife "can bear her own weight, which is a big step, I think. Just speaking for the doctors here, I think she's made a remarkable recovery at this point."
He said he believes she has tried to speak, although she is prevented from doing so by a breathing tube in her neck, and believes she is aware of her surroundings, saying he can look in her eyes and tell. She will smile at him and pat him on the face -- something she did before the shooting, he said.
"Every time I interact with her, there's something quite inspiring," he said.
"We've seen her moving her lips," acknowledged Dr. Michael Lemole, chief of neurosurgery at the hospital. But, he said, it's hard to say whether Giffords is actually trying to speak.
He said Giffords has been able to scroll through an iPad and interact with her husband, so she does appear to be aware of her surroundings.
But, Lemole cautioned, she has a long road ahead of her that will take months, at least.
Kelly has discussed the shooting incident with Giffords, Rhee said. "She can probably put some of that information together on her own."
Kelly said he believes his wife would be proud of how the Tucson community has reacted to the shootings. "She's going to need to continue to be strong," he said. "She will really appreciate the support of this community."
He said Giffords' family looked at several different rehabilitation facilities and liked Memorial Hermann for several reasons. The medical team there specializes in penetrating head injuries like the one Giffords has suffered, and its closeness to Tucson is also helpful.
Giffords has undergone other "minor procedures" this week, Lemole said, calling it "housekeeping. It's really getting her to a position where she can graduate from this hospital."
Investigators have charged Jared Lee Loughner in the attack. A federal grand jury indicted Loughner on Wednesday on three charges of attempted murder. The indictment charges Loughner, 22, with attempting to kill Giffords and two of her aides, Ron Barber and Pamela Simon.
Legal experts said that more federal charges against Loughner are likely.
"This is really a placeholder indictment," CNN senior legal analyst Jeffrey Toobin said Wednesday. "The grand jury investigation will continue; there's a long way to go in this case and these charges will be there but I'm certain there will be more as well."
Loughner is next set to appear in court on Monday in Phoenix.
"I don't think we're ever going to fully understand the whys and the how and, you know, the reason for what happened on the 8th of January," Kelly told reporters. "It's a loss of innocent life. The injury of a dozen people, the death of a 9-year-old girl, a federal judge and the serious traumatic injury to my wife Gabrielle -- we'll never fully understand that."
CNN's Paul Vercammen, Susan Candiotti and Roni Selig contributed to this report