The better regionals (meaning the ones with better contracts) have 2 hour call outs. At ExpressJet we have 2 types of reserve, short call and long call. They have slightly different rules but the main difference is that short call is 2 hour call out and long call is 12 hour call out. I believe the contract stipulates that 10% of the reserve lines have to be long call lines. Depending on where you live, it is possible to sit long call reserve at home but be careful with that, heard of a few guys getting burned.