Why doesn't the exterior design of passenger planes change a lot?

-You can notice a difference in the exterior of some passenger planes, however passenger planes look so similar. I still think planes are amazing examples of engineering, especially passenger planes. I remember my recent holiday waiting at the airport for a plane. When one plane arrived at the airport i wondered how something so big could do what a plane does.Mostly all reasonable answers. A note on blended wing aircraft entering development lately: there were 'lifting body' designs, similar to 'blended wings', back in the '20s and '30s, developed by a visionary designer Vincent Burnelli. His theories, inventions and developments were thwarted by a lot of controversial vested interests and politics in the day. There were indications that the concept would be significantly more crashworthy than the current tube-on-wing configuration. Plenty about Burnelli on the web... visit http://www.burnelli.com and also http://en.wikipedia.org/wiki/Vincent_Burnelli
What we have now works very well so it hasn't been worth gambling billions of dollars on a revolutionary change. Instead what we have is a series of small refinements, winglets for example. Nevertheless a technological revolution is coming. Blended wing bodies are just around the corner. There have been wind tunnel tests and free flight model tests. Full scale designs are on the drawing boards or should I say in the computers.
It's a well though out, thoroughly engineered,and tested shape. Over the last 60 years, there have only been small changes to the overall planform and proportions. I'd say That speaks pretty well for those Boeing and Douglass engineers from the 40s and 50s.



As one answer said, "if it ain't broke, don't fix it"
because its an already efficent design. remember, "if it aint broken, dont fix it"
Because it works.



There are significant differences, if you know what to look for. M
It's a tried and true design.



"If it ain't broke, don't fix it!"
because they all ready work fine
Largely because aviation power plant technology has not undergone any dramatic changes.in decades, and the laws of aerodynamics don't change at all. Aircraft design is a function of the mission and operating envelope the plane is intended for. Dramatic changes in aircraft design have always been driven by major changes in engine technology.

The turbofan engine has been in use for more than 20 years, and while they have been produced in ever larger and smaller sizes and grown more efficient, their optimal operating envelope has not changed. They work best in high subsonic cruise at altitudes between 25,000 and 40,000 feet. The basic design that works at that speed while offering the most opportunity for turning a profit looks like a Boeing/Airbus.

Variations on the design are mainly do to ground considerations. Regional airliners normally have to offer the ability to load using internal "air stairs" , so they use rear mounted engines to allow the plane to sit lower. Military transports take that further by using a high wing design that offers greater protection from debris to the engines.