You may not be able to fly on a United flight if the name on your ticket does not match your passport name. A small correction may be made without additional charges to the passenger according to United Airlines Name Change Policy.
If you've booked a Delta Airlines ticket but want to change your name after arriving at your destination, you need to know their Delta Airlines Name Change Policy.
American Airlines Normally Doesn’t Permit Any Name Changes After a Ticket is Booked, except for very minor spelling corrections or a name change due to marriage. Here are more details you should know about the American Airlines Name Change Policy:

https://www.travelintellect.com/united-airlines-name-change-policy/
https://www.travelintellect.com/delta-airlines-name-change-policy/
https://www.travelintellect.com/american-airlines-name-change-policy/