In essence, a speaker who dies on the way to the conference is no different from a speaker who has to cancel because of a reason other than death, like a family emergency, illness, injury, logistical problem,... and there are already articles on this subject.
I am going to quote relevant parts here from https://www.mpiweb.org/blog/article/4-ways-to-handle-event-speaker-no-shows because this is effectively what you're faced with: a no-show.
- Always have a “Plan B.”
When planning your event, create a list of speakers you have worked with in the past and keep their contact information in your event file. When you have an existing relationship with a speaker they will usually be very willing to jump in to help you if their schedule is open. Keep in mind the geography of where your event will be held and make the list accordingly based on where speakers live. When interviewing speakers to hire for your conference, ask them about their plans in case of an emergency. While you never want to get that call from your speaker saying they are too ill to speak to your audience, if they have already found a fantastic solution it will make your day much better. (Speakers who are members of the National Speakers Association can tap into this network no matter where in the world they are scheduled to speak.) A few years back I received a call from a speaker who was scheduled to present at a conference in my hometown who had a bad case of food poisoning. There was no way he could go on stage, but he remembered I lived in Austin, Texas. Since I was available the speaker had a possible solution before the organizer even knew there was an issue.
- Look to your event agenda
A multi-day industry event will have a full docket of speakers who will already be present at your conference. Look to see whose program could be upgraded from a breakout to a keynote. If it is a breakout session you need to fill, see if the keynote speaker has additional content that can be delivered as a “booster shot” for those who might want more from his or her main stage program (some speakers will charge you for the extra presentation, but most will be happy to step in and help you out in your time of need). A friend of mine who was scheduled as the opening keynote speaker at an event was recently asked a week ahead time to stay for two days and also deliver the closing keynote because the final speaker had a family emergency. Problem solved, and they created consistency in the opening and closing bookend presentations.
- Create an interactive expert panel
Your audience is full of brilliant people. Select two or three topical questions that are cutting-edge and involve timely issues within your industry. Enlist your master of ceremonies or a leader in your organization to be the facilitator and explain openly and honestly about how the speaker could not be there. Proclaim this to be a fantastic and unique opportunity to crowd source knowledge and best practices. Have a panel of two or three people talk about the issues and allow the attendees in the crowd to share their input. Make the audience the heroes and have a high-level, interactive discussion.
- Make it a networking opportunity
Turn the speaker-less session into a “Networking Speed-Dating Bonanza” by encouraging people to make more contacts. A main reason people attend live events is for the networking opportunities, and most meeting organizers admit that no matter how much time they schedule for people to mingle, people often want more chances to meet others on site. Make this space in your agenda a facilitated experience to foster powerful connections. Do not be timid or overly apologetic in explaining the changes to the agenda. Leadership by the meeting organizers is paramount to success in a situation where you need to adjust your program on the fly. Confidently communicate to the attendees that the keynote speaker canceled, and be honest about the reason. Let them know that with their support and participation the meeting will still have an equal or greater impact than was planned.
Beyond the issue of dealing with the no-show itself, there are also some other things specific to the situation of a death. Academia usually is a pretty tight community, so there are bound to be other people at the conference who know the deceased in some way.
- It is probably a good idea to start the time slot of their presentation with a moment of silence.
- If multiple people died (as happened in the XX International Aids conference in 2014 after MH17 was shot down), a candlelight vigil or other memorial event can be appropriate, as well as dedicating part of the opening ceremony to honor those that died. Both of these things were done by the aforementioned conference.
- You may want to give those stricken with grief a way to deal with that grief, like providing grief counseling to whoever needs it.
- Provide condolence books onsite for those who wish to dedicate a few words to the dead. After the conference, send these books to the relatives of the deceased along with whatever else is appropriate for the culture of the deceased (usually flowers, but this may vary).
- If the payment for the presentation hadn't yet been delivered to the deceased before his death, it's usually appreciated by the family to donate this to a charity. An obituary for the deceased may mention which charity, but if that's not the case, a charity related to the conference subject is probably the most appropriate.