Coastal HF radar in the ground-wave mode may be useful for monitoring the movement of ships, aircraft and icebergs over vast areas of ocean. At HF frequencies an aircraft is in the `resonance range' of size. The paper studies the radar cross-section (RCS) of a 30-m aircraft-like object for nose-on and broadside incidence, by direct measurement and by wire-grid modelling, with good agreement. The `generic aircraft' RCS is demonstrated to be dominated by the vertical stabilizer at low HF frequencies, but by the fuselage for broadside incidence at higher HF, in level flight. Resonant effects in the RCS are related to resonant-length paths on the airframe. It is shown that a wire antenna carried for HF communication can introduce sharp resonance peaks and troughs into the aircraft RCS. The changes in RCS due to nose-up and nose-down flight attitude, and to steep banking are briefly investigated.