(CNN) -

Former President Bill Clinton said that AIDS researchers among the 298 killed when a Malaysia Airlines jetliner was shot down over eastern Ukraine on Thursday were "doing so much good."

"Thinking about those people, knocked out of the sky, it's pretty tough," Clinton added in an interview Friday with CNN's Anna Coren.

A number of members of the International AIDS Society were on the plane as they made their way to a major conference in Melbourne, Australia, according to a statement from the organization. The former president is scheduled to give a keynote address at the conference next Wednesday.

"This gathering, we do this on a regular basis, have these international AIDS conferences. And I try to go to all of them because I'm always so inspired by what other people are doing and what we can learn from them," Clinton said in Hanoi, Vietnam. "Since I left office it's been kind of a regular part of my life. Thinking about those people, knocked out of the sky, it's pretty tough."

Clinton is in Hanoi as part of his tour of Asia/Pacific countries to review the work of the Clinton Foundation.