Most every company (at least those that base pilots out of a hub) builds some sort of day trip lines (the number and value vary). It's a necessity to allow for the best utilization of the pilot group and staffing numbers.

Most of the time they go very senior. Personally I disliked them since you don't earn any untaxed per diem and it took me about 2 hours of commuting each day when you factored in the time to get to/from employee parking, through security, and out to the terminal (and I lived 5 miles from the parking lot)...