Roughly 12,000 researchers, delegates, and others were expected in the city for the five-day meeting, dubbed AIDS2014, which helps fuel the battle against one of the world’s most pervasive diseases.

Former U.S. president Bill Clinton is scheduled to speak, as is musician and activist Bob Geldof and UNAIDS executive director Michael Sidibé. Landing those speakers likely took a lot of footwork.

What was unplanned: The surge of grief and shock over the loss of researchers onboard Malaysian Airlines flight MH17, which was shot down over Ukraine yesterday.

Nearly 300 people were killed in the tragedy, including renowned Dutch AIDS researcher Dr. Joep Lange and dozens of others headed to the conference. Their loss cast a long shadow not only amongst their loved ones and colleagues, but over an event designed to celebrate recent progress and provide inspiration for the next few inroads against HIV and AIDS.

Event planners know to expect the unexpected, and risk management is part of that equation. Yet no one can plan for airplane disasters, even if it’s something we consider on a personal level each time we buckle our seatbelts before takeoff. In fact, AIDS 2014 organizers considered canceling the conference — until they reasoned that their colleagues would want them to go on.

Have you ever had to cope with a tragedy that impacted your event? If so, we’d be interested to hear how you navigated the grief and shock that such losses bring while having to make practical decisions. And to all those aboard MH17: You will be greatly missed and our thoughts are with your family and friends, and your colleagues in Melbourne.