Some observers believe that there will be such growth in the travelling public and such constraint on airport and airspace usage that, by early in the 2000s. very large passenger carrying aircraft will be required. By ‘very large’ is meant anything from 1,000 to 2,000 seaters. Whilst the problems which come to mind when musing on this possibility are mostly those of ‘passenger flow’ in the widest sense and rather less related to the vehicle itself, there are some issues related to the vehicle which suggest themselves. One is the choice of fuselage cross section.

Because cabins have to be pressurised (10 psi is a typical figure for cruise altitudes up to say 40,000 ft), it has been the norm to utilise circular cross sections (or double-bubble type) since the pressure forces are contained by hoop loads only, without frame bending, which affords a light and fatigue-insensitive structure (Fig. 1).