There's one detail that trips up more BA claims than anything else: you have to explicitly ask for EC261/UK261 compensation, not just file a general complaint.
Submit via British Airways' "Flight cancellation compensation" page under their Legal/Help section, referencing EU261 or UK261 by name depending on your route, your booking reference, flight number, and the amount you're claiming based on flight distance.
If you booked with BA but the flight was operated by a different airline (a codeshare), the operating airline is responsible for compensation, not BA. Check your boarding pass for the actual operating carrier before filing — this is a common source of claims being redirected or delayed.
£220 for flights under 1,500km, up to £350 for medium-haul, up to £520 for long-haul delays of 4+ hours (reduced for 3-4 hour delays on long-haul routes). Amounts are fixed regardless of your fare class or ticket price.
Our letter explicitly cites the regulation and amount — exactly what BA needs to see.
Check my flight free