MOUNTAIN VIEW — A California Air National Guard unit based out of Moffett Field is in the midst of a mission to save a 1-year-old girl in medical distress aboard a sailboat drifting far off the coast of Mexico, authorities said.

The guard received a call from the U.S. Coast Guard late Thursday morning reporting that the American infant was seriously ill and in need of medical attention that could not be provided by family members aboard the 36-foot sailboat “Rebel Heart.”

The boat is about 900 nautical miles offshore, and the Coast Guard contacted the 129th Rescue Wing of the guard, which has the capability to reach the remote destination, said 2nd Lt. Roderick B. Bersamina, spokesman for the wing.

The plan is to drop four medically trained parachuters and Zodiac inflatable boats out of a long-range Lockheed MC-130P aircraft into the ocean near the sailboat. The medics will board the sailboat and provide immediate aid, and on Friday a helicopter will be sent out to the craft — refueling in midair along the way — to bring the girl to a medical facility on shore.

Around 9 p.m., Bersamina said rescuers had boarded the vessel and were getting the infant’s vital signs to transmit them to a doctor on the airplane above. The examination was still under way an hour later, although they had determined that the girl was in stable condition.

“One other significant thing they discovered is that the sailboat has no power and no capability of steering itself,” said Bersamina.

He said that means the team is formulating a plan to extract all four family members — the distressed infant, another child and their parents.

“But right now the focus is on the child,” he said. “It’s all about getting the vitals and having them diagnosed to make sure she gets the medicine she needs.”

He did not have specifics about what is wrong with the girl, only that she is severely ill.

He said the “Rebel Heart” is confirmed to be a U.S.-based boat, but did not know what port it hails from.

The guard is determining whether more rescue craft might have to be employed to get all family members to safety, if necessary. But he said it is possible that they could get the boat moving on its own.

“Right now it doesn’t have power, but that could change,” he said.

A second large, four-propeller MC-130P is slated to leave Moffett on Friday morning to join the HH-60G Pave Hawk rescue helicopters grouping in Cabo San Lucas, Mexico, for the second part of the mission.

The main mission of the 129th Rescue Wing is performing wartime duties to recover personnel from anywhere in the world. The wing has also completed an array of missions to rescue civilians, including people with medical issues aboard ships and lost or injured hikers, as well as disaster response.

Bersamina said the wing is credited with saving the lives of more than 1,000 people.

Check back for updates to this story.

Contact Eric Kurhi at 408-920-5852. Follow him at Twitter.com/erickurhi.