Beginning July 1, Executive Club members will have the option of booking a ticket using miles and cash. So, instead of spending 50,000 miles for trip from North America to the U.K., members will now be able to redeem just 35,000 miles, as long as they’re willing to part with a little green. Once the program begins, British Airways will install a calculator on its Web site showing exactly how much cash is needed for various award types.