PORTLAND (AP) - Two sisters who attend the University of Oregon were aboard a jetliner that was missing in Indonesia, family members said.

Stephanie Jackson, 21, and Lindsey Jackson, 18, both from Bend, were visiting their father, 54-year-old Scott Jackson, a wood-products industry representative who lives part time in Indonesia, Brazil and Oregon, family members told The Oregonian newspaper Tuesday.

The Jackson sisters and their father were believed to be the only Americans aboard the flight operated by Indonesia-based Adam Air.

The plane sent out two distress signals in stormy weather Monday. Contrary to an earlier report, no wreckage has been found despite a search over land and sea.

Stephanie Jackson is a senior majoring in pre-med, and Lindsey Jackson is studying marine biology, their mother, Felice Jackson DuBois of Bend, told the newspaper.

“Any time I hear that they're going on an airplane, yes, I'm scared,” DuBois said. “But you can't live your life guided by your fears. You just want to hold out hope.”

DuBois said her daughters sent her an e-mail that said “Happy New Year” shortly before takeoff.

DuBois, who is divorced from Scott Jackson, described her daughters as adventurers who have lived and traveled overseas since they were young.

Scott Jackson is president director of P.T. Fendi Mungil, an Indonesian manufacturing company that makes rattan furniture, said Sheryl Webb, the company's international sales manager.

The plane carrying 102 people sent out two distress signals in stormy weather Monday halfway through its two-hour journey from Indonesia's main island of Java to Manado, on the northern tip of Sulawesi, one of the largest islands.

Initially, officials said 12 people had been found alive at a crash site on Sulawesi's mountainous western coast. But rescue teams hiking into the rain-soaked jungle found nothing. The government later recanted the reports, saying the earlier statements had been based on the unconfirmed accounts of villagers.

“It's hard to ferret out the rumor from the facts,” DuBois said. “All we can do is wait.”

DuBois described Stephanie as “tenacious,” and recalled a time when the family was living in the Portland suburb of West Linn. A stack of freshly cut oak was sitting in front of their house, and her father told Stephanie, then in first grade, she should try to sell it.

“She went out and sat on that pile of wood with a for-sale sign the entire day,” DuBois said. “She sold it all. Whenever you would give her something, she was like a dog with a bone. She just wouldn't let up on it.”

Lindsey Jackson, meanwhile, has always loved nature.

“There'd be a butterfly here, a beetle there,” DuBois said. “We always say that animals don't understand that she's human. She had an affinity for the natural world, and we always said she was a walking insectorium.”

The Jackson sisters graduated from Summit High School in Bend. Both ran cross country and Lindsey Jackson threw the javelin for the track team, track coach Dave Turnbull told The Bulletin newspaper of Bend.

“There are some kids out there who everybody likes because they're genuine, they're sincere,” Turnbull said. “They were good athletes and good kids.”

In her high school yearbook, Lindsey Jackson wrote that her future plans were to: “Solve world hunger by living on a boat studying the ocean.”

That would be in character, said Katie Linthicum, 16, who went to prom in a group that included Lindsey. “She was one of those people who if she said she was going to change the world, you would completely believe her,” Linthicum said.