Each new model change usually brings improvements over earlier models. From the point of view of increasing window area and designing more pleasing appointments, there have been significant advances.With regard to engine reliability and time between overhauls, significant advances have also been made.Solutions to some of the other problems, however, have made little gains. Examples are pilot sitting position and ease of seeing outside the cockpit area; noise level for effective verbal communications between instructor and student; and shoulder space for instructor and student in trainers.An area where major strides are yet to be made is in panel, cockpit, instrument, and control layout and function. A continuing concern expressed by pilots is the transition time from one aircraft to another or the problems of regularly operating in two or more aircraft. This suggests that there is a need to provide more commonality between airplane layouts.Since the hourly maintenance labor costs are increasing, the original design should consider labor-saving methods during routine inspections such as accessible location of battery.Performance data and aircraft systems descriptions should be more uniform between manufacturers.