At ABX Air (DHL America) it's "week-on, week-off" in theory, with lots of variations. Most lines have 7-8 day blocks of flying twice per month. Each block is a series of day layovers (fly hub to destination early AM and back to hub in PM, with 3-5 hours at hub each night). Most blocks include a weekend layover, mostly Sat to Monday but a few Friday to Monday or Saturday to Tuesdays (YYC is a four day!). There's a lot of other trips/lines out there but this covers about 75% of our flying.