>>One major company has (had??) a policy restricting the number of senior officers who could fly on one flight. For lesser officers and managers, a larger number was permitted. Finally the lowest-ranked had a still larger number.
>>But no such restriction was placed on bus, rail, or boat travel.
Logical, as air-incidents, though rare, are frequently total losses, whereas the other travel methods rarely invoke mass demise. It's called not putting all your bags in one exit. They aren't prohibiting air-travel per se.