That's why AC and other airlines instituted their weekend sell-off web specials. And you will often find TANGO fares close to flight date within Canada. However, selling midweek seats at a discount within days of flight is still not a practical consideration for airlines, even if seats are empty. They know there is a demand for last minute seats which, because they are there when the customer needs to go, are offered at a premium. Were airlines to discount prices within days of flight, why would anyone book earlier if they had a few hours of flexibility in their schedules?