Short answer: not much, yet. Here's what changed, what didn't, and why it might matter for your specific flight.
When the UK left the EU, it copied EU261's air passenger rights rules almost word-for-word into UK domestic law, where they're now commonly called "UK261." The core protections — compensation for long delays, short-notice cancellations, and denied boarding, at the same three distance-based tiers — are essentially unchanged. What's different is which flights each regime covers, who enforces it, what currency you're paid in, and the fact that UK261 is no longer legally required to track future changes to EU261.
EU261 covers flights departing an EU/EEA airport on any airline, or arriving at one on an EU/EEA-based airline. UK261 covers flights departing a UK airport on any airline, or arriving at one on a UK or EU-based airline. A flight from London to New York is a UK261 matter; a flight from Paris to New York is an EU261 matter; a flight from London to Paris can potentially engage both, depending on direction and airline.
Under EU261, each EU/EEA member state designates its own National Enforcement Body. Under UK261, that role sits with the UK Civil Aviation Authority (CAA), which handles complaints and oversees ADR schemes for UK-related claims.
EU261 compensation is set in euros (€250 / €400 / €600 by distance band). UK261's published amounts were converted into pounds sterling at the time of transposition and can be updated independently by the UK going forward — so a sterling figure should always be checked against current guidance rather than assumed to be a fixed conversion.
This is the one that matters most long-term. Before Brexit, EU261 was shaped by rulings from the Court of Justice of the EU (like the technical-fault cases discussed elsewhere on this site), and the UK courts had to follow that same case law. Post-Brexit, UK courts are no longer bound by new CJEU rulings on retained law, and the UK government isn't obliged to mirror future amendments the EU makes to EU261 itself. In practice the two regimes have stayed closely aligned so far, but there's no guarantee they'll stay identical forever.
Plenty of common routes — London–Paris, Dublin–Manchester, Amsterdam–Edinburgh — can potentially fall under either regime depending on direction of travel and which airline operated the flight. Where there's a genuine overlap, the practical approach is to work out which regime gives you the clearer or stronger claim rather than trying to invoke both for the same disruption.
It depends on where your flight departed and landed, and which airline operated it. A flight departing a UK airport is generally covered by UK261; a flight departing an EU/EEA airport is generally covered by EU261; some routes can fall under both.
UK261 uses the same three-tier distance structure, but pays out in pounds sterling rather than euros, and the specific published sterling amounts should be checked against current CAA guidance rather than assumed.
You generally can't be compensated twice for the same disruption, but on routes where both could apply, it's worth checking which regime gives the stronger or clearer claim.
Not necessarily. Since Brexit, the UK is no longer required to mirror future changes the EU makes to EU261, or follow new rulings from the Court of Justice of the EU, so the two regimes could diverge further over time.
Tell us your route and we'll work out whether EU261, UK261, or both apply.