JoAnne Shirley said her brother, Maj. Bobby Marvin Jones, is believed to have gone missing at Bach Ma Mountain in South Vietnam on November 28, 1972. Jones, whom Shirley describes as a “great” older brother with whom she had “a very close relationship,” was 27 years old and had only been in the U.S. Air Force for about two months at the time the F4D aircraft he was traveling in disappeared from radar.

Through the nearly 49 years that have passed since Jones’ disappearance, Shirley has played an active role with the National League of POW/MIA Families, serving for nearly four decades as the coordinator for her home state of Georgia and for more than 10 of those years as the chair of the league. She has been on delegation trips to visit Southeast Asia—flying directly past Bach Ma Mountain on one—and has testified before Congress about the challenges involved with service member recovery efforts.

Previous excavation teams sent over the last 25 years to survey Bach Ma Mountain have not uncovered Jones’ remains, but one that traveled to the area in 2008 did succeed in finding Jones’ blood chit, which is a message Jones is believed to have been carrying at the time of his disappearance that identifies him as an American service member in several languages and includes a number assigned specifically to him.

Thirteen years after that excavation crew found Jones’ blood chit, Shirley told Newsweek she had hoped another trip planned to start last month would have better luck in recovering evidence of her brother.

“We’ve kind of been in limbo all these years,” Shirley said during a conversation with Newsweek last month. “But to get the blood chit when Bobby had been missing 36 years was miraculous.”

Prior to joining the Air Force, Jones graduated from the University of Georgia and the Medical College of Georgia, after which he completed a one-year internship at Baylor University Hospital in Dallas, Texas. Shirley said Jones had a “very low” draft number, so he decided to join the Air Force before beginning his residency.

“He thought he’d probably have four years’ residency, and he didn’t want to get in there and be pulled out to be sent over for the Vietnam War,” she said.

In September 1972, Jones was sent to Udorn, Thailand, where he served as a flight surgeon. He wasn’t a pilot, Shirley said, but he needed to log time in the air in order to retain his role.

On the day Jones went missing, he was flying in the backseat of the F4D with pilot Jack Harvey of Florida from their base in Udorn to Da Nang, South Vietnam. When they were about 20 miles out from their destination, their plane dropped off the radar.

Nearly five decades later, Shirley said it is still unknown if her brother’s plane was shot down or if it clipped the top of the mountain as he and Harvey flew past.

According to the POW Network’s entry for Jones, there may have been multiple prison networks in the area where Jones and Harvey disappeared, but “if Jones was captured and kept in another system, the POWs who returned did not know it.”

Both Jones and Harvey are included on the Defense POW/MIA Accounting Agency’s list of the more than 1,500 American service members still unaccounted for from the Vietnam War.

The latest excavation trip initially planned to take place in August and September was to be the first in the area in about three years, according to Shirley. Aside from the blood chit, search teams have previously only found airplane debris.

“They were going to expand the excavation on both sides of what they’d already done down the whole mountain slope,” Shirley said of the 2021 team’s plan.

Though Vietnam was initially considered to be one of the most effective nations at combatting the pandemic, the recent spread of the Delta variant has prompted lockdowns within the country amid spiking infection rates. Shirley said she was told the virus posed too great a risk to the Americans and Vietnamese who would have worked in close proximity if the trip had proceeded as planned.

“On one hand, I totally understand,” Shirley said. “I don’t want to risk their lives, either. But I’m so disappointed because I felt like this might be my last chance.”

Shirley said her contact at the U.S. Department of Defense said the earliest the postponed excavation trip could be rescheduled would be “well into 2022.” A spokesperson for the Defense POW/MIA Accounting Agency (DPAA) told Newsweek the agency could not make any firm plans until the coronavirus situation improved.

Shirley told Newsweek she is worried the excavation trip won’t be rescheduled.

“I don’t know another reason they’d be motivated to go back again—they’ve done the whole mountain slope,” she said. “I don’t know what would bring them back after this.”

Though the trip’s timeline remains in question, Shirley has continued to raise awareness about Jones and the work of the National League of POW/MIA Families. Earlier this week, she delivered remarks about her brother virtually during the DPAA’s annual government briefings, which are intended to keep families of POW and MIA service members updated on their recovery efforts. The briefings began on Wednesday, just two days before the National POW/MIA Recognition Day on Friday.

Shirley mentioned the postponed excavation trip during her virtual appearance at the DPAA’s Wednesday briefing and said she is hopeful it will be rescheduled for 2022.

“This year, on November 28, 2021, Bobby will have been missing for 49 years,” Shirley said. “And I’m just hoping and praying that we someday will be able to bring him home to honor him for his service and his sacrifice.”