A. Transfer Partners
American Express, Chase, Aer Lingus, and Iberia are 1 to 1 transfer partners with British Airways. American Express typically offers a transfer bonus of 25-40% once or twice a year.
You can also transfer from Marriott at 3 (Marriott) to 1 airline point transfer ratio. You can also get an additional 5,000 airline points bonus if you transfer in increments of 60,000 Marriott points. (e.g., 60,000 Marriott points become 25,000 airline points, whereas if you only transfer 59,000 Marriott points, you would only get 19,667 airline points)
Other Partners: Hilton HHonors: 10:1, Hyatt Gold Passport: 2.5:1, IHG Rewards Club: 5:1, and Le Club Accor: 2:1.
B. Flying with British Airways and Partners
British Airways has an online mileage calculator for both British Airways flights and flights on their partners.
C. Credit Cards
Chase British Airways
Application Link (Target: 100,000; Current: 100,000)
Annual Fee: $95
Earning: 3x at British Airways and 1x everywhere else.
Benefits: No foreign transaction fees, secondary rental car insurance, baggage delay insurance, 120-day purchase protection, and lost luggage reimbursement.
Verdict: The British Airways card is a great card to keep for exactly one year. The bonus is usually quite good but requires a high minimum spend. Additionally, British Airways points are worth above 2 cents per points, so putting regular spend on the card is a good idea. However, the card lacks other benefits to justify a $95 annual fee.
D. Other Ways: