AMSTERDAM — As the airport lounge filled with passengers waiting to board Malaysia Airlines Flight 17, a renowned professor rushed to the gate while texting a colleague, saying that he was “superbusy.”

Veering into the business-class line, Joep Lange, an AIDS researcher, passed a former election observer who had just returned from Ukraine. They were among 298 passengers and crew aboard the flight, which was shot down over Ukraine on Thursday.

The disaster claimed the lives of a number of people headed to the International AIDS Conference, scheduled to begin on Sunday in Melbourne, Australia, the International AIDS Society said on Friday. Dr. Lange, 59, was accompanied by his partner, Jacqueline van Tongeren, 64. He was the executive scientific director of the Amsterdam Institute for Global Health and Development, and she worked as a communications director there.