On December 28, 2020, the Federal Circuit vacated the PTAB’s decision that found Raytheon’s patent was not unpatentable for obviousness. The PTAB found that Raytheon’s patent for a two-stage high pressure turbine engine for commercial airplanes was not obvious in view of the prior art’s one-stage high-pressure turbine. The PTAB believed that the prior art disclosed but taught away from the two-stage engine option. The Federal Circuit disagreed and found that the prior art’s teaching does not support a teaching away from a two-stage engine. The prior art did not define a single-stage turbine as a “critical” or “enabling” technology, but rather a system benefit that cannot be implemented into an advanced engine without successful development of other “critical and enabling” technologies. Further, the prior art did not make a single negative statement about the use of a two-stage high-pressure turbine or discourage the use of a two-stage high-pressure turbine. For that reason, substantial evidence did not support the Board’s conclusion that the prior art taught away from modifying the prior art’s ADP engine to include the two-stage option.