GE's Flying Test Bed recently celebrated its 40th Birthday, having rolled out of the Boeing Everett Factory on October 17, 1969 as the 25th 747. Most likely the oldest 747 still actively flying in the US and one of the oldest in the world. She has tested all new or updated GE, CFMI, and EA commercial engines since 1993 from the CF34-8 to the GE90-115B. According to press releases, the future is busy with GEnx-2B testing this year and CFM56-7BE testing next year.
Official press release from GE:
Seems neither the mainstream nor the aviation media picked up on the story.
Happy Birthday N747GE!