Kotlin, what is class delegation all about

ClassicComposition.kt

class Aircraft(
    private val liftMechanism: Flyable,
    private val propulsion: Movable
): Flyable, Movable {

    override fun fly() {
        liftMechanism.fly()
    }

    override fun move() {
        propulsion.move()
    }
}

PolymorphismThroughComposition.kt

class Aircraft(
    liftMechanism: Flyable,
    propulsion: Movable
): Flyable by liftMechanism, Movable by propulsion

interface Flyable {
    fun fly()
}

class FixedWing: Flyable {
    override fun fly() = print("Adjust wing angle..")
}

class RotaryWing: Flyable {
    override fun fly() = print("Start spinning the blades..")
}

class HotAir: Flyable {
    override fun fly() = print("Start floating..")
}

interface Movable {
    fun move()
}

class Unpowered: Movable {
    override fun move() = print("Just hanging up here..")
}

class Propelled: Movable {
    override fun move() = print("Starting engine..")
}

PolymorphismThroughInheritance.kt

interface Aircraft {
    fun fly()
    fun move ()
}

interface WingedAircraft: Aircraft {
    override fun fly() = print("Adjust wing angle..")
}

interface RotorCraft: Aircraft {
    override fun fly() = print("Start spinning the blades..")
}

interface AerostatsAircraft: Aircraft {
    override fun fly() = print("Start floating..")
}

interface UnpoweredVehicle: Aircraft {
    override fun move() = print("Just hanging up here..")
}

interface PropelledVehicle: Aircraft {
    override fun move() = print("Starting engine..")
}

class Glider: WingedAircraft, UnpoweredVehicle
class Jet: WingedAircraft, PropelledVehicle
class Gyroglider: RotorCraft, UnpoweredVehicle
class Helicopter: RotorCraft, PropelledVehicle
class Balloon: AerostatsAircraft, UnpoweredVehicle
class Zeppelin: AerostatsAircraft, PropelledVehicle