Creating Flying Enemy:

In this article I will try to describe one possible way how to create 'flying enemy' - lets some kind of bird. In most cases you will need physics as well, that's why first thing you have to do is to decide what kind of body will you use (for body types description - CHECK HERE)

In our example we want to create 'FLYING' enemy that's why don't need gravity for our monster body, it means KINEMATIC body type will be most suitable. Our monster will constantly move will along the X axis (changing direction, right - left)

• Create new Entity - for example AnimatedSprite.
• Create new Kinematic Body for previously created entity.
• Register new PhysicsConnector
• Override onUpdate()

final float maxMovementX = 200;
final Sprite m = new Sprite(x, y, width, height, textureRegion);       
m.setCullingEnabled(true);
final Body b = PhysicsFactory.createBoxBody(physicsWorld, m, BodyType.KinematicBody, wallFixtureDef);
b.setLinearVelocity(-1 * 5, 0);
       
physicsWorld.registerPhysicsConnector(new PhysicsConnector(m, b, true, false)
{
    @Override
    public void onUpdate(float pSecondsElapsed)
    {
        super.onUpdate(pSecondsElapsed);
               
        if (m.getX() <= x - maxMovementX)
        {
            b.setLinearVelocity(b.getLinearVelocity().x * -1, 0);
        }
        if (m.getX() >= x + maxMovementX)
        {
            b.setLinearVelocity(b.getLinearVelocity().x * -1, 0);
        }
    }
});

With this easy way, our monster will constantly move, changing his direction after getting to the certain point (in this example his starting X value plus maxMovementX variable or minus, in the left direction) We are changing his movement direction, by multiplying his X linear velocity by -1. Obviously its only basic implementation, most likely you will need to set user data to check contacts between bodies in CONTACT LISTENER - to handle for example dying of player or killing the monster.