The most straightforward way is to call and ask. While they won't give you specifics, most airlines will tell you if there are business class seats available, and whether economy is full. Another way to find out is by logging into the airline website with your booking number.

Moving from Economy to Business Class can be achieved through several methods, ranging from guaranteed purchases to "luck-based" tactics. The most straightforward way is to manage your booking on the airline's website or app and pay the "fare difference." Many airlines also offer a "Bid for Upgrade" system where you can name a price you are willing to pay for a premium seat; if the airline has empty seats a few days before departure, they may accept your bid. You can also use frequent flyer miles or "Upgrade Certificates" earned through elite status. For a more "economical" approach, check the airline app exactly 24 hours before your flight during the check-in window, as airlines often offer significantly discounted last-minute upgrades. Finally, while "free" operational upgrades are rare, you can increase your chances by traveling alone, being a loyal member of the airline's rewards program, and simply arriving early and politely asking at the check-in counter if any paid or points-based upgrades are available for that specific leg.