From personal experience, I can say that most drug companies who pay for the airfare of physicians to go to meetings, cover economy class seats for intracontinental North American flights, and also Caribbean flights (including Bahamas or Bermuda), and business class seating for transoceanic (ie Atlantic or Pacific Oceans) flights.

Novartis seems to be one exception - it pays for business class tickets, even for domestic or transborder flights.