What are the factors behind increasing aircraft window sizes?
In the early years of the jet age, which followed closely on the introduction of pressurized hulls, there was much fear of stresses specifically in the area of the window openings due to the loss of two DeHavilland Comets. Subsequent Comet hulls had different shaped, rounded, smaller windows and that trend continued in other pressurized, typically jet-powered, aircraft.



Only with modern CAD systems and new materials knowledge could windows be made larger again. The newest aircraft designs reflect that progress.