There are two kinds of QF-4s. The first is NULLO Full-Scale Aerial Target which keep the above basic drone conversions. For the 82d, NULLO means Not Under Live Local Operation. A NULLO flight always required at least three drones, the one to be shot down, a spare and a manned QF-4 flying as chase plane. The second kind were manned full-scale drones fitted with advanced countermeasure systems installed by the USAF. While some of the twin-stick QF-4s retained their dual control system as trainers and both ejection seats in working order, the other manned QF-4s have the rear cockpit ejection seat removed. All NULLO aircraft have both ejection seats removed. Noticeable differences between the two are the six antennas from the VDOPS scoring system, the hump on top of the fuselage, a crude box on the left intake and a fairing in the left forward Sparrow III missile well.