What's happened? Some parts of the wing are missing!
But, don't worry. That part is removed for the maintenance. What the mechanics removed was fuel tank. This type of fuel tank is called " integral tank" which constitute a part of wing.
It is very convenient for the maintenance. It is easy to remove and easy to install.
The picture below is the tank itself. It is placed upside down. There is a fuel drain valve from which you drain the fuel during pre-flight inspection.
