Southwest reserves
I don't work for them and have no direct knowledge of this but I could see it.
The fly a single type and almost all their routes are high frequency so covering a sudden shortage is relatively easy. Pilots and management get along, the employees all pull together so helping out in a bind is company trait. With correct staffing levels and good rostering you will only need reserves to cover the unexpected. Why pay pilots to sit reserve if you can manage without it?
20driver