Not at my airline. Unless you're willing to pay of course!
If we need to upgrade, the lucky pax who this happens to will have been pre-dermined before you've even left the house to get to the airport.
Operational Upgrades will always go to gold frequent flyer members first, or passengers on corporate accounts.
As a check in agent the most monotonous question we're asked is 'Are there any free upgrades available?'
Thos days are long gone!!!