Originally Posted by
FlightDetective
All bookings on British Airways with BA flight numbers that are operated by Aer Lingus have a standard 10kg carry on bag and a 20kg hold bag included.
You can ignore anything on the Aer Lingus website as its systems are not designed to display the information correctly when it comes to a BA codeshare services.
Therefore you have nothing at all to worry about. The Aer Lingus staff are well versed with these as there are many passengers each day flying on the BA booked Aer Lingus flights, so you will be fine.
Is it 20 Kg or 23 Kg? According to BA's site and other flyertalk postings, the checked baggage allowance for codeshares is 23 Kg (and hand baggage per the operating carrier's rules).