To upgrade from Premium Economy to Business or Signature Class on Air Canada in 2026, you have several primary paths. The most common is the AC Bid Upgrade, where you can offer a cash amount or Aeroplan points starting from the time of booking up until 48 hours before departure; if accepted, you are notified roughly 48 hours out. Aeroplan Elite Status members can use eUpgrade Credits, which offer a more predictable path if "R" class space is available. You can check this availability using tools like ExpertFlyer or by looking for the "eUpgrade" icon during the booking process on Air Canada's website. If seats remain, a Last Minute Upgrade Purchase may be offered during the check-in window (starting 24 hours before flight) for a fixed cash price. Finally, if you hold miles with a Star Alliance partner (like United or Lufthansa), you can request a Star Alliance Mileage Upgrade, though these are subject to strict fare class requirements and capacity controls.