B-24s, in particular, were subject to significant changes. These changes were intended to camouflage the aircraft during the night service; on the other hand, they reduced the armament and made it more vulnerable to enemy attacks. The set of changes to each aircraft was not standardized; over the months, there was a great variety of combinations.
The most important change consisted in the removal of ventral turret (or ball turret), which left a circular hole on the fuselage, where a liftgate was mounted. The hole was suitable for the launch of supplies and agents; for this reason it is known to history as ‘Joe’s hole’, so named because of the custom of the OSS to refer to its secret agents with the codename ‘Joes’ (‘Janes’ or ‘Josephines’ in the case of women, mostly radio operators).
Sometimes the front turret was removed as well; in its place a large transparent window was installed to allow the bombardier to benefit from better visibility.
In the bomb bay, instead of bombs, special racks were installed to hold British made C-type containers. The latter, entirely made of steel, were automatically dropped with the same mechanism used for bombs. The goods packed in non-standardized wraps were stored in the rear section of the fuselage, and were launched manually from the dispatchers through the Joe’s hole.
Airplanes were painted with all-black camouflage paint (matt at the beginning, glossy at the end) to reduce their visibility in the night sky .
The aircrafts were completely blacked out by installing special curtains; in this way the internal lights strictly necessary for flight and navigation could continue to be used without filtering outside of the fuselage.
The B-24s for special operations and in particular those belonging to the 885th BS were equipped with the most advanced electronic flight technologies available at that time. Among other very special equipment there was the ‘Rebecca’ , whose presence aboard was revealed by a pair of additional antennas visible on opposite sides on the outside of the fuselage, at the navigator’s compartment position.
B-24 42-63980 of the Carpetbagger unit (801st/492nd BG), 858th BS pictured in 1944 with Sgt. William T. Alexander, engineer.
The front turret had been removed and additional antennas for the Rebecca equipment had been installed .
Flame arrestors devices were installed on the engine exhaust vents to minimize their visibility at night, taking a small decrease in power. On the mouths of defensive weapons flame arrestor were installed as well, to hide the glow to the night fighters.
Oxygen cylinders intended for crew were often removed, being unnecessary as missions were conducted at low altitudes.
Many other minor changes were made on the aircrafts; in general, all the devices dedicated to bombing and not necessary for special missions were removed.
 Warren (1947), p. 38 – 40.
 Moore (1992), p. 45.
 Macpherson et al., (2010), p. 34; MacCloskey (1966), p. 29.
 MacCloskey (1945).
 The ‘Rebecca/Eureka’ system was the forerunner of modern navigation systems and involved the use of an electronic ‘Eureka’ apparatus on the ground, on the dropping zone, repeating a signal and acting as a radio beacon, and of a ‘Rebecca’ device, mounted on board of airplanes approaching. ‘Rebecca’ was equipped with a pulse transmitter and a receiver, which performed a telemetry of the distance and the direction of the ground counterpart, visible on a screen. ‘Eureka’ was equipped with a self-destruction device to be used in case of need. Rebecca and Eureka Equipment, Chapter 2 (1943).
The system, although having a limited range of about 30 miles (48 km) was of help, especially in bad weather conditions, so one could make the drops through the clouds. MacCloskey (1966), p. 327.
The effectiveness of the entire system, however, seems not to have been definitively established. MacPherson (1945), p. 57; Condit (1954), p. 4.
 The Carpetbagger Photographic Archives & Historical Research Center. 801st/492nd BG (Carpetbaggers) Association. Ogden, Utah, USA.