> There's a bigger risk from them taking the bus to the conference
The risk to an individual attendee of dying in a bus accident on the way to the conference is certainly higher than the risk of dying in an airplane crash on the way to the conference.
However, the risk of 100 of them dying if they all take the same flight is almost certainly higher than the risk of 100 of them dying in bus accidents on the way to the conference (even if they stay together and all travel in the same bus). Even very bad bus accidents in cities in first world countries tend to leave many more survivors than fatalities.
The risk to an individual attendee of dying in a bus accident on the way to the conference is certainly higher than the risk of dying in an airplane crash on the way to the conference.
However, the risk of 100 of them dying if they all take the same flight is almost certainly higher than the risk of 100 of them dying in bus accidents on the way to the conference (even if they stay together and all travel in the same bus). Even very bad bus accidents in cities in first world countries tend to leave many more survivors than fatalities.