I really have come to HATE United. I fly to Mexico City to spend time with my partner 4 - 5 times a year. United has the only real directs from Dulles to Mexico City.
Now, after you PAY to upgrade from Basic Economy to Economy (so you can reserve a seat), you have to PAY $29/flight to reserve an aisle seat OR $19/flight to reserve a window seat. And, if you want any real leg room you have to PAY more.
Hate United... hate their bring your own devise policy because their too cheap to upgrade their cabins; hate their nickel and dime you to death pricing policies.
Give me Delta ANY TIME.