Students from the University of Virginia have proven that 3D printed parts can indeed result in a real aircraft. The two students, 3rd year engineering students on an internship with Mitre corp, designed and manufactured an airplane with a 6.5 foot wingspan that flies as a UAV, or unmanned aerial vehicle. This type of aircraft is extremely versatile for everything from wolf population studies to covert bombing missions, and being able to quickly manufacture specialized UAVs with 3D printing technology is a goal of the US Defense Department.
STEM students who have access to manufacturing with 3D printers in your classroom should be inspired by the utility of this design, particularly its size. While 3D printers have a relatively small build envelope (typically 4 to 6 inches square) careful design can allow for much larger structures with smaller components fitted precisely together into a larger piece.
According to this article from U of Va, this is only the third known 3D printed airplane to have been built that has actually flown. It achieved a speed of 45 mph. Of note for STEM teachers is a discussion of how the 3D printers in the U of Va rapid prototyping lab are used as real world teaching machines. If you are hesitating to spend your hard fought budget on CNC machines of any type for your class room, the time to get your students on board is now. The plane is leaving the runway.