I know the rules for a large German chemical company:

Paid F for the executive committee and for division heads (of which there are about 40).

Paid C for the next level down (about 400 employees).

Paid C on flights above 4 hours for the next level down (no idea how many people).

Everyone else flies coach.

Exceptions are made if you're flying with customers and the customers are booked into a higher service class than you. However, your travel then requires approval from higher-ups (including from your division head for travel in F).

If you're travelling on company business with someone from the company who is entitled to a higher class of service than you, you can fly the class they're flying if they approve it and let it be charged to their cost centre.