Well spotted, StopStart.
The image credit from the RAF Waddington Facebook page is 'USAF via RAF Waddington'. Photographed at L-3's facilities in Greenville, Texas.
The reflection on the starboard side clearly shows a v-shaped logo. The winged USAF symbol?
Link to Offutt RC-135 showing intake cover.
USAF Boeing RC-135W Rivet Joint 62-4138 KDMA by James O'Rear acm1208 | Flickr - Photo Sharing!