Not enough AAdvantage miles for an award? American's new cash and miles option can help

American Airlines is giving its AAdvantage program members a new way to spend their miles. Over the coming weeks, eligible members will be able to pay for select flights with a mix of cash and miles on aa.com and in the American app.The move brings American in line with rivals including Delta Air Lines, United Airlines and Southwest Airlines, which already offer some form of cash and miles bookings. It could be handy if you have a small balance of American miles you can't otherwise use. But American hasn't said what each mile will be worth redeeming them in this new way, and the option wasn't live in our accounts when we tested it.Here's what you need to know.Related: Combination of points and cash: How I strategize my award redemptionsHow cash and miles bookings workOnce the new option is live, eligible U.S. AAdvantage members will be able to book domestic cash flights on American, excluding flights to and from Alaska and Hawaii, and then choose how many AAdvantage miles they wish to redeem to reduce the cash cost of the flights.Unlike searching for an award booking, you won't need to select the "Redeem miles" button when searching for a flight, and it won't depend on traditional ...