A number of prominent charitable organizations state that gifts of frequent flyer miles are generally not tax deductible, because they are given to you by the airline and therefore have no monetary value in the eyes of the Internal Revenue Service.
You can contact the IRS at 800-829-1040 for a decision as to whether your gift would qualify as a deductible non-cash charitable contribution on IRS Form 8283 Noncash Charitable Contributions.