I have a marriott rewards card for hotels. We stay in enough Marriotts to make it worth while. I also have that same card tied to Delta restaurants for which then gives me both airline and hotel miles on one transaction. I've been here 2 years in February and have earned just over 240k Delta miles. I have miles on AA and UA but living in the southeast I use Delta more often when vacationing. when you start commuting you're able to send in your mileage rewards numbers for all the Airlines and it will automatically show up on your reservation. Typically I can look at my reservation on my Delta App before I even Hangup the phone with the travel office. I then pick my seats on my own.