No, in 2026, UK aviation regulations and airline policies strictly prohibit passengers from consuming their own alcohol during a flight. While you are generally allowed to carry alcohol purchased in duty-free onto the plane, it must remain sealed in its original retail packaging for the duration of the journey. Airlines like British Airways, easyJet, and Ryanair explicitly state that only alcohol served by the cabin crew may be consumed on board. This rule exists for safety and legal reasons; cabin crew are trained to monitor alcohol intake and manage intoxication to prevent disruptive behavior. Violating this rule can lead to the confiscation of the alcohol, and in severe cases, you could face a fine of up to £5,000 or even a prison sentence upon landing in the UK.