Originally Posted by SparseFlyer

The "after departure" likely refers to the handling of the change. After departure, changes are made based on historical fares. Before departure, if changing the outbound or more, new fares apply.

Usually the fare rules are very explicit about the SDC costs. Can you post it here please?

Also, SDC rules are flat fee only (if applicable), and no fare difference. As long as the flight is not overbooked. If flight is J1 Y-1, you are not allowed to SDC (why allow someone to change free if it's going to cost you an $800 IDB). If flight is J1Y1, the flight may still be overbooked (RM willing to overbook at $2K one way, but not $75).

Also, it's good practice to never assume that fare rules are "similar" or "standard" for international flights. It varies wildly. Even the price is not an indicator (you could have free SDC on a $2K P fare to Europe but not on a $5K Z to the same destination).

Within NA though, Domestic and TB rules with their one way pricing have been standardized, so it's very easy to deal with. But any international, always check, and if you're on a net/bulk fare, always be prepared to pay.