Leviathan is a boss from 1941: Counter Attack. It is fought during mission 3 and again during mission 5.
Details[]
The Leviathan is a large bomber of twin-boom design. It doesn't have much airfoil surfaces to generate lift and is largely dependent on propulsion provided by its two massive engines, each driving a four-blade propeller, and two rocket boosters to stay airborne. The Leviathan has five machinegun turrets, two located outboard each fuselage boom and one turret under the central fuselage, and one barrage balloon dispenser. The central fuselage turret will start firing after the other four are destroyed. The bomber must be taken out piece by piece before going for the cockpit.
A second Leviathan is commissioned to a enhanced design (presumably after the destruction of the first one and hence no efforts being made to distinguish between the two machines) and deployed against the player(s) in Mission 5. The new Leviathan sports proper wings and two smaller engines in the fuselage booms, each driving not only four-blade propellers to their front but also two pairs more before the tailplane assembly, while the two larger engines from the original design are moved outboard into their own nacelles along with extra rocket boosters. In addition to the five machinegun turrets inherited from the old design, the outboard engine nacelles have their own barrage balloon dispensers and ventral turrets whereas each fuselage boom has mounted a twin flak cannon turret. It attacks in the same manner as the original, except harder due to having more weapons and being much more proactive in their use, and is taken out in the same manner.