Usually you find these kinds of figures in articles about 3D printing aircraft parts. For example, "By reducing an airplane’s weight by just one kilogram, an airline can save $1,300 in fuel costs per year, according to the [2011] IBISWorld report." [1] The 2014 report can be purchased here [2]. Of course, these numbers will depend on the kind of plane and its utilization, as well as fuel costs.

[1] http://www.businessweek.com/technology/3d-printing-coming-to...

[2] https://www.ibisworld.com/industry/3d-printer-manufacturing....