On the most memorable of such occasions.....mine were put down in a Truck Stop and told to call a Taxi.....which they gladly did. A bit of Severe Turbulence connected to a Frontal Passage on a bright clear day and their Pilot's warning that the flight could be done as it was within both the aircraft and Pilot's capability but the ride would be extremely off putting.
They insisted as they just had to be the other side of the mountains for a Meeting.....a routine monthly meeting....that could really have been done over the telephone.
They never challenged a "No" Decision after that.
The Corporate Mentality was to fly Single Engine Helicopters and Cessna Caravans over mountainous terrain at night and IMC for the Airplane.....with the caveat that a Twin Engined aircraft would only take you to the scene of the crash following an engine failure.
I made my opinion known about that and was fired within a week.
A few months later a King Air and Beech Jet showed up.