Yes, you can upgrade with Avios after booking your flight on British Airways, provided there is Reward Flight availability in the next cabin. This is one of the most popular ways to use points in 2026. You can typically upgrade a cash booking by one cabin—for example, from Economy (World Traveller) to Premium Economy (World Traveller Plus), or from Business (Club World) to First. To do this, you log into "Manage My Booking" on the British Airways website, select your flight, and look for the "Upgrade this flight with Avios" option. It is important to know that the lowest-priced Economy fares (specifically those in fare classes Q, O, and G) are generally excluded from Avios upgrades. The "cost" in Avios is the difference between the Reward Flight price of the cabin you booked and the cabin you want to move into. You will also be responsible for paying any difference in taxes, fees, and carrier charges, which can be significant on long-haul routes. If no space is available, you can set alerts using third-party tools to notify you if an upgrade slot opens up before your departure.