The problem of late war aircraft appearing in 1941-2

[el cid again]

There is a time bomb in the data set created by stock. To the extent
it is not reworked with respect to air groups, it is present in all mods.

This is an intermittent issue with respect to any given air group.
It ONLY appears IF the air group is withdrawn, disbanded or wiped out
by enemy action. And it also only happens if the given air group has a
pointer in the "return as" field.

IF a unit is disbanded (in any sense), AND IF the unit points at
a different group in its return as field, THEN it WILL ALWAYS reappear
in ONE day. It will appear precisely as the return as group is defined.

It seems that the original data entry people were told, or assumed, that
if there is a date in the air group, that has priority. It does not work
that way: the date a unit appears is IGNORED if the unit is pointed at
as a "return as" group.

Most of the time the return as group has late war aircraft.

This problem will go away if you get rid of the return as field. Better,
redefine the return as group so that it returns with planes from the same
period as the original group, and UPGRADES to later war types. As well,
make sure the return as group is of the original size, and resizes exactly
as the original group did.