Another Dash 9 rebuild program, this time between BNSF and GE, is aiming to create A-1-A AC-traction units. BNSF 616, a former ATSF C44-9W was shipped off to the GE shop in San Luis Potosi, Mexico back in early 2014. The unit received extensive rebuilding including an overhauled 7FDL-16 prime mover, AC traction equipment, and new A-1-A trucks. BNSF's goal is to create A-1-A "AC4400CW's" out of the 600-series of C44-9W's. Units 599-619 round out BNSF's current AC44C4M fleet. There are currently no plans for more at this time.
Note: #666 was renumbered to 599 long before that C44 entered the program. It retains #599 after rebuild.
See unit #600 on its way home: https://www.youtube.com/watch?v=dCM8pjRfED0
See the unit back in 2014. http://www.rrpicturearchives.net/showPicture.aspx?id=3924370
See the 616 in action in this video: https://www.youtube.com/watch?v=fP_0A6E7Oz8