Left: a finder’s chart for the positions of interest in the Cep E protostellar outflow: Spitzer-IRAC band-two (4.5 μm) image, retrieved from the Spitzer archive. Grey circles mark the diffraction-limited SOFIA beams at the frequencies of [OI]_63μm (smaller circles) and CO (16–15) or OH at 1838 GHz (larger circles) lines. The three observed positions are indicated (Cep E-mm, red star, BI and BII, white rectangles), as well as others in the red lobe (RI and RII). The knots denomination is from Gómez-Ruiz et al. (2012). Right: zoom on the southern lobe of the outflow showing the spatial components identified by L15 in CO (2–1) (see Sect. 3): the jet (cyan contours), the terminal bow-shock (yellow contours distant from the protostar) and the cavity walls (coloured background). The three observed positions are indicated with a white star, and the SOFIA beams at the frequencies of [OI]_63μm (smaller circles) and CO (16–15) or OH at 1838 GHz (larger circles) lines are shown in BII.