Ward and Robert Zimmerman were brilliant. They were adventurous, physically fit and full of love for family.

That is how Everett’s Ruth Brandal remembers her father and uncle, brothers in their 80s whose cross-country airplane trip ended in tragedy earlier this month.

Together, they had flown often in Robert Zimmerman’s small plane, a 1963 Mooney M20C. Last year, they even flew to Brazil, where Robert Zimmerman, 84, had worked as a physics professor and most recently lived.

Brandal, the daughter of retired Boeing design engineer Ward Zimmerman, 86, said their last trip began April 14. Her father lived in south Seattle, and the plane was hangared near Kent. With stops to see relatives along their route, they flew as far as Fredericksburg, Virginia, before heading back west.

Brandal’s brother, also named Ward Zimmerman, lives in Virginia and spent a happy week with his father and uncle. “They were having a great time,” said Ward Harry Zimmerman, 64.

By May 1, they had left Virginia. Brandal, an Everett nurse, said they stopped to see their sister in Iowa, then cousins in Nebraska and Wyoming. Their plane was last seen May 6 taking off from Yellowstone Regional Airport in Cody, Wyoming, according to The Associated Press.

“Based on maps, they made it about 30 miles to the mountains, and crashed,” Brandal said.

According to news reports, both men are believed dead based on aerial views of the crash site, which is at the 9,900-foot level of 10,964-foot Mount Howell. The peak is in northwest Wyoming near Yellowstone National Park. In Cody, a Park County Sheriff’s Office spokesman was quoted by the AP as saying no recovery effort would be made until avalanche danger ends, which could be weeks.

Brandal, who works in the intensive-care nursery at Everett’s Providence Pavilion for Women &Children, said memorial services won’t be held until the men are found. In the meantime, the family is grieving and remembering two remarkable men.

Brandal and her husband, Paul, own and live on property that many remember as the “buffalo farm.” They still have one bison, a 22-year-old named Wobble. From 1992 to 2005, they kept a herd and called their business Bisondalen. They sold bison meat and hides, and at times hosted school tours.

“Dad helped us wrangle the buffalo, when we had to separate calves or get them ready for shipment. He loved doing that,” Brandal said.

Her brother, Ward Zimmerman, said their father was born in Dupree, South Dakota. The elder Ward Zimmerman attended the South Dakota School of Mines and Technology and the University of Wisconsin. He served in the U.S. Navy, which sent him to flight school.

His older brother, Robert, had earned a doctorate in nuclear physics at the Massachusetts Institute of Technology. “They were brilliant men,” Brandal said. Robert Zimmerman taught at Alabama Agricultural and Mechanical University in Huntsville, and at a university in Sao Paulo, his nephew said.

Ward Zimmerman, who retired from the Boeing Co. in 1987, worked at a number of Boeing sites. His son and daughter said he was responsible for several patents. They included an electronic propulsion control system on the Boeing 757, an attitude system for space vehicles and a development that increased the time satellites could maintain communications.

Robert Zimmerman is survived by his wife, Adelaide. Ward Zimmerman’s wife, Elynor, died two years ago.

A faithful member of Seattle’s Emmanuel Anglican Church, Ward Zimmerman helped his community in many ways. He and his wife had been foster parents to 26 children. They had adopted the youngest two in their family of six children.

In retirement, he was a volunteer driver with the Group Health Transportation Assistance Program. “Whenever he wasn’t out flying, he would drive our seniors to their medical appointments. His riders just loved him,” said Lisa Hirohata, the program’s coordinator. “He was a great model for healthy aging,” she said.

He volunteered doing home repairs through a church program, his children said, and regularly read to children at Mercer Island’s Lakeridge Elementary School. He also had worked part-time at McLendon Hardware in Renton.

Brandal said both men were healthy, fully credentialed, experienced pilots. Not long before the crash, they had decided one day not to fly because of bad weather on the East Coast. The family doesn’t know which man was piloting the plane.

Ward Zimmerman worked out five days a week on a treadmill, said his daughter. Her father had a weakness for lemon pie. Before coming back to Seattle, the brothers planned one more stop. A granddaughter lives in Estacada, Oregon, southeast of Portland. “She had made him a lemon pie. He never made it there,” Brandal said.

She and her brother are glad the brothers spent their last days together, and with loved ones. With their sister, the men had taken a cruise to Alaska last June. “They had all these fresh, happy memories of their adventures together,” Brandal said.

“They lived every day,” her brother added.

Julie Muhlstein: 425-339-3460; jmuhlstein@heraldnet.com.