"Wet wing is a technique of housing fuel in an aircraft in the wing and this technique is heavily used in large planes to help reduce wing flutter and balance weight on the aircraft. Wet wing is a great design as it eliminates the need for separate bladders or tanks on the aircraft and saves a ton in the overall weight of the plane. From a safety point of view, they are advantageous if a leak were to happen because leaking fuel doesn't discharge to a populated section of the plane. Like any design though, there are some disadvantages to utilizing a wet wing design. First and foremost is the need for every item to be sealed to prevent fuel from leaking around hardware components and the sealant's need to consider expansion from temperature changes."