Here’s a handy tip if you’re one of the travelers who have to manage a lot of travel related account information such as frequent flier mile numbers, hotel and car rental account information, etc. A convenient way to store this information while slimming your wallet at the same time is by storing it in your mobile phone’s address book.
You can enter each airline’s name in the Name field and keep your account number in the Note field, which is alphanumeric unlike the phone number field.
Read more about this here:
Travel tip: store frequent flyer numbers in your smartphone’s address book