Yellowstone is a Boeing Commercial Airplanes project to replace its entire civil aircraft portfolio with advanced technology aircraft. New technologies to be introduced include composite aerostructures, more electrical systems (reduction of hydraulic systems), and more fuel-efficient turbofan engines (such as the Pratt & Whitney PW1000G Geared Turbofan, General Electric GEnx, the CFM International LEAP56, and the Rolls-Royce Trent 1000). The term "Yellowstone" refers to the technologies, while "Y1" through "Y3" refer to the actual aircraft.
Yellowstone is divided into three projects:
- Boeing Y1, to replace the Boeing 737 product line. Y1 covers the 100- to 200-passenger market, and is expected to be the second Yellowstone Project aircraft to be developed. If launched, it will compete with the Bombardier CSeries and the planned Airbus NSR family.
- Boeing Y2, to replace the Boeing 767 product line. It may also replace the 777-200. Y2 initially referred to the highly efficient, more conventional, baseline aircraft for the Sonic Cruiser, which was project "Glacier". It has now been built as the 787 and covers the 220- to 320-passenger market. It will compete with the Airbus A330, A340 and later A350 families.
- Boeing Y3, to replace the 777-300 and 747 product lines. Y3 covers the 300-400+ passenger market, and is expected to be the third Yellowstone Project aircraft to be developed. It will compete with the Airbus A380 family as well as the largest model of the A350 family, the A350-1000, which will be introduced in 2015.