They do. For Instance
On Everyday but Saturday:
Southwest Airlines flight 2852
PHX-
MDW Departs 5:05pm arrives 10:30pm
On Saturday
Southwest Airlines flight 1365
PHX-
MDW Departs 5:00pm arrives 10:00pm
On Everyday but Saturday
Southwest Airlines flight 2255
PHX-
MDW Departs 6:50pm arrives 11:55pm...
Just for example, I'm sure there are many more. Those are all scheduled...
BMIa330