Three proposed aircraft designs have varying levels of success in meeting tough NASA goals for reducing fuel use, emissions and noise all at the same time. (Credit: NASA)

The Boeing Company's advanced design concept is a variation on the extremely aerodynamic hybrid wing body. Image credit: NASA/Boeing

Lockheed Martin's concept uses a box wing design and other advanced technologies to achieve green aviation goals. Image credit: NASA/Lockheed Martin

Northrop Grumman's concept is based on the extremely aerodynamic "flying wing" design. Image credit: NASA/Northrop Grumman

Read: New Ideas Sharpen Focus for Greener Aircraft.