Yes, but how do I add this unit or any unit for that matter, to the game?
You guys should add biplane unit. Sorry x2 post thought I opened my first post.
You can edit the xml files like civ4, or use the civ5's way,
backup you xml files first if you edit it.
Civ4 - Rabbit,White 's "How to add units, a guide."
You need edit these files : (this will use the "tank" to example)
C:\Program Files (x86)\Steam\steamapps\common\sid meier's civilization v
1. \resource\Common\civ5artdefines_unitmembers.xml
Find the tag "ART_DEF_UNIT_MEMBER_TANK", copy everything between the tag <UnitMemberArtInfo> and </UnitMemberArtInfo>,
then change the tag <Type> to another name, e.g."ART_DEF_UNIT_MEMBER_TANK_XXX".
change the tag "<Granny>Assets/Units/tank/tank.fxsxml</Granny>" to new added .fxsxml file.
2. \resource\Common\civ5artdefines_units.xml
Find the tag "ART_DEF_UNIT_TANK", copy and rename it like step 1, rename the tag <MemberType> too.
The tag <MemberCount> is how many units to display.
3. \Assets\Gameplay\XML\Units\CIV5UnitClasses.xml
(Skip this step if you don't add the new classes)
4. \Assets\Gameplay\XML\Units\CIV5Units.xml
Find the tag "UNITCLASS_TANK", copy everything between the tag <Row> and </Row>,
then change the tag <Type> to "UNIT_TANK_XXX" and change the <UnitArtInfo> to step 2 's name, e.g."ART_DEF_UNIT_TANK_XXX".
(This XML can modify the units Ability.)
5. \Assets\Gameplay\XML\Civilizations\CIV5Civilizations.xml
Fnd the tag <Civilization_UnitClassOverrides> to add the new unique unit.
<CivilizationType> What civilization you want to add the new unique unit, e.g. CIVILIZATION_AMERICA, CIVILIZATION_ENGLAND...
<UnitClassType> For this example, change to "UNITCLASS_TANK"
<UnitType> Change to "UNIT_TANK_XXX"
Sorry my bad english.