"bulge". Two of the compartments would be liquid loaded in order to disrupt the gas bubble of a torpedo warhead detonation while the bulkheads would elastically deform and absorb the energy. Due to the external armor belt, the geometry of the "bulge" was more similar to that of the North Carolina class rather than that of the South Dakota and Iowa classes. Like on the South Dakota and Iowa classes, the two outer compartments would be liquid loaded, while two inner ones be void with the lower Class B armor belt to form the holding bulkhead between them. The greater beam of the Montanas would allow a higher system depth of compared to of the North Carolinas. Until the authorization of the Montana class, all US battleships were built within the size limits of the Panama Canal. The main reason for this was logistical: the largest US shipyards were located on the East Coast of the United States, while the United States had territorial interests in both oceans. Requiring the battleships to fit within the Panama Canal took days off the transition time from the Atlantic Ocean to the Pacific Ocean by allowing ships to move through the canal instead of sailing around South America. By the time of the Two Ocean Navy bill, the Navy realized that ship designs could no longer be limited by the extant Panama Canal and thus approved the Montana class while simultaneously planning for a new third set of locks that were wide. This shift in policy meant that the Montana class would have been the only World War II–era US battleships to be adequately armored against guns of the same power as their own. Aircraft The Montana class would have used aircraft for reconnaissance and gunnery spotting. The type of aircraft used would have depended on when exactly the battleships would have been commissioned, but in all probability, they would have used either the Kingfisher or the Seahawk. The aircraft would have been floatplanes launched from catapults on the ship's fantail. They would have landed on the water and taxied to the stern of the ship to be lifted by a crane back to the catapult. Kingfisher The Vought OS2U Kingfisher was a lightly armed two-man aircraft designed in 1937. The Kingfisher's high operating ceiling of made it well-suited for its primary mission: to observe the fall of shot from a battleship's guns