Boeing saw the huge success of A380 spuerjumbo in 2008, so they decided to develop a new superjumbo called B797, which is to be delivered in 2014.
They decided the B797 should be of twin-engined design for better fuel economy compared to A380. The B797 is solely powered by two newly developed GE180 160,000-180,000lb class engines. It has fan tip diameter of 160in and engine cowl diameter of 180in, almost at large as cross-section of B767, the largest turbofan engine ever.
Because of this, there is only 12in (0.3m) of ground clearance from the engine, the smallest in the world.
Boeing conducuted the first flight of B797 in 2012. But the aircraft tilted to the left on landing at Ancourage because of strong side wind. The left engine touched with the ground first instead of the wheels. Some sparks generated, and all people in the aircraft had to evacuate because of possible fire generation.
This makes all airlines ordered B797 cancalled the order and switched to A380 because B797 has its engines so close to the ground, so there is very high change of engine being toched with the ground instead of the wheels, thus creating dangers for its passengers.
Boeing had no choice but totally change the design of B797 to 4-engined design, with each enging being about 80,000lb thrust, so to get the order again. This, however, costs Boeing extra 20 billion US dollars, and makes Boeing B797 has to be delivered as late as 2020, 14 years after first delivery of A380, and 6 years behind of the schedule.