American Express Membership Rewards members can receive 40 percent bonus miles when transferring Membership Rewards points to British Airways Executive Club miles through March 31, 2011. You can only earn the bonus once and keep in mind that British Airways adds a fuel surcharge to award tickets that may cost you a few hundred dollars. Membership Rewards points normally transfer into Executive Club miles at a ratio of 1:1 so 1,000 points will transfer into 1,400 miles with this bonus offer.