detectability by radar, which is not necessarily
    proportional to its physical size.  (See also  low
    observable technology.
RAM   Radar Absorbent Material.
RCS   Radar Cross Section.
recon   Reconnaissance.
red shirt   A deckhand who handles ordnance on an
    aircraft carrier.
redout   A loss of vision (or consciousness) due to pulling
    too many negative g's.
remote magnetic indicator   RMI -- Aircraft instrument
    that displays heading information and magnetic bearing
    to one or two radio beacon stations. 
Rhino    Unflattering nickname for the F-4 Phantom II.
RIO   Radio Intercept Officer -- The rear-seat weapons
    and navigation specialist in the F-14 Tomcat and F-4
    Phantom.
ROE    Rules Of Engagement -- Rules governing the
    conditions under which a fighter can engage or fire upon
    an unidentified aircraft.
ROK   Republic of Korea, also known as South Korea.