The 298 passengers and crew members aboard Malaysia Airlines Flight 17 on Thursday were from at least 10 countries. Some were flying for business trips, others for adventure, to move abroad or to visit relatives. One man was traveling to his mother’s funeral in Jakarta, Indonesia.

Few, if any, probably had any idea that the Boeing 777’s flight path would take it over a hotly contested area of Ukraine.

More than 100 of those on board were researchers headed to an international conference on HIV-AIDS.

The tragedy struck a particularly terrible blow to the world’s community of HIV-AIDS researchers and activists, who are gathering in Melbourne, Australia, for next week’s 20th International AIDS Conference.

President Obama said Friday that they were “men and women who had dedicated their own lives to saving the lives of others, and they were taken from us in a senseless act of violence.”

Among them was Joep Lange, the former president of the International AIDS Society and a world-renowned pioneer of antiretroviral therapy, a treatment that has helped save countless lives.

Glenn Thomas, a spokesman for the World Health Organization, also was traveling to the conference when he died on Flight 17.

The crash also claimed the lives of parents and grandparents, children and toddlers, students and businesspeople.

The State Department confirmed at least one American fatality on Friday: Quinn Lucas Schansman, a U.S.-Dutch dual citizen. He was flying to Malaysia to join family members on vacation there.

Schansman’s Facebook profile says he was studying in Amsterdam at the International Business School.

Karlijn Keijzer, a 25-year-old Dutch doctoral student in chemistry at Indiana University, had just prepared a computer simulation on a drug used to treat cancer and Alzheimer’s disease before catching the flight for a vacation with her boyfriend.

Described as a brilliant student by faculty and staff members at Indiana University, Keijzer also was a formidable athlete. She rowed on the varsity eight boat and helped the university’s women’s rowing team earn a 14-5 record during the 2011 season.