The low seat inclination and low leg room in passenger aircraft is a great discomfort to passengers particularly, during long haul flights. Addressing this will mean reducing the number of passengers, particularly those in the economy class by about half. This however will result in high ticket prices. If there is a way of designing an aircraft in which passengers can sleep on adjustable flat seats while paying for ticket prices comparable to that of an ordinary passenger aircraft, then this problem of fatigue and discomfort can be solved. Available experience indicates that passenger comfort depends largely on the length of legroom than cabin height. Therefore, reducing the cabin height to a reasonable level while increasing the seat spacing in an aircraft can serve as a way of increasing passenger comfort without extensive additional cost.

What is being proposed is therefore a twin-engine wide body passenger jet with a double-decker cabin, whereby the cabin height in each deck is comparable with that of a narrow body aircraft. The seat pitch in each cabin is about twice that of existing passenger aircraft. The cabin diameter of the proposed aircraft (Fig.1) is 5.85 m, which is almost the same as that of some existing wide body aircraft like Boeing 777, etc. The height of each deck is about 2 m with 8 abreast seating in the upper deck and 10 abreast seating in the lower deck. The seating pitch in each deck is about 1.6 m, which is about twice that of existing passenger aircraft. With this arrangement, half of the passengers in a single-decker aircraft can occupy each deck therefore increasing leg room and enabling flat adjustable seats for passengers to sleep (Fig. 2). Analysis shows that the additional fuselage shell material volume due to two floors in the double decker aircraft is about 1.3 times that of the fuselage in a single decker aircraft with the same fuselage size. This translates to about 3 % increase in cost of the entire aircraft with the plausible assumption that the fuselage cost constitutes about 10% of the aircraft cost. It is therefore envisaged that passengers will be willing to pay for the low comparative additional marginal cost and enjoy the comfort of increased legroom as well as being able to sleep on a seat arranged flat like a bed during the flight therefore making therefore making the operation of the proposed aircraft economically feasible.