Instead of installing glass windows in a jet, Technicon employed the use of special cameras for its IXION airplane. The design uses these cameras to make it look like the roof and side of the plane are actually windows looking outside (in reality they are simply screenshots).
It's hard to tell whether or not this experience would be exhilarating or absolutely terrifying. Looking out of a small window seems to be quite a safe option, but having an entire roof looking out on the space above and clouds below would produce a completely different range of emotions. The entire design is still a concept right now, but the technology is available to build the XION jet if Technicon wanted to go forward with the project.
Photo Credits: designboom, technicondesign