FlyerTalk Forums - View Single Post - Same Day Changes (SDC) and Free Change on the Day (FCOD) on BA tickets
Old Jun 13, 16, 10:57 am
Join Date: Aug 2013
Posts: 7,713
It can be any coach seat - doesn't need to be in the same fare class. You can make the change from midnight on the day of departure. It has to be changed at least one hour before your original departure.

Note that it's only available on direct flights, not connections.

More details from the BA trade website:

Originally Posted by BA
Free flight changes on the day of departure:

Flights can be changed on the same day for free to an earlier or later available flight. The customer’s original flight and the flight they change to must both be within 00:00 and 23:59 local time of the departure airport. At least one hour’s notice must be given prior to the scheduled departure time.
The routing (origin and destination airports) must remain unchanged. Routing or date changes made on the original day of departure may incur fare and/or tax differences, as usual.
Changes are subject to availability on the new flight in the same cabin as the original flight.
Ldnn1 is offline