Can I Change My Already Booked Flight With British Airways?
These free flight adjustments must be made at least an hour before the scheduled departure time of your original trip and can only be made the day of travel, not the night before.

Similar to the original flight, your new flight must have the same routing and make stops at the same airports.
The same airports in each city must be used for both takeoff and landing.
In the same vein, even if taking a connecting flight will get you to your destination faster, you won’t be able to change your nonstop travel.
Finally, you won’t be able to switch to an earlier flight if you have already checked in for your original departure.
Therefore, this was all about changing or canceling your flight. If you wish to know more about it or if you have to change your ticket, you can call us now.
Source Url- https://thewion.com/can-i-change-my-already-booked-flight-with-british-airways/
Visit- https://manageairlinesbooking.com/blog/how-to-book-multi-city-flights-on-delta-airlines/