A program that measured the in-flight RF spectrum on 37 revenue flights of commercial aircraft cabins is described. The spectrum monitoring was performed from gate-to-gate in selected aviation critical and personal electronics frequency bands over the period from September 23 through November 19, 2003. The commercial aircraft in-flight RF environment for two critical navigation frequency bands, VOR and Global Positioning System (GPS) and four consumer electronics frequency ranges are reported. A brief analysis of the GPS band data is presented.