Until the allied landing of Salerno in September 1943 (operation AVALANCHE), the only special flights to Italy were intended to parachute secret agents and to supply allied Prisoners Of War (POW) behind enemy lines .
The four-engined heavy bombers used in special missions were the American Boeing B-17 Flying Fortress and Consolidated B-24 Liberator, as well as the British Handley Page Halifax and Short Stirling. They flew alone, at night, in absolute radio silence and without any escort, often in very adverse weather conditions. The success of the mission depended solely on the skill and on the technical training of the crew, added to some amount of luck.
Some of the target areas were located in the most mountainous regions of Europe. From the point of view of the ground reception parties, it was preferable for the dropping zones to be protected by mountainous walls along all sides. These characteristics, which facilitated the task of those who were to receive the launches, were also deadly traps for any aircrew who had not received adequate training. The pilots had to learn to lead their aircrafts at low altitude and low speed. The B-17 and B-24, when they come close to the target area, had to slow down to speeds between 120 mph (193 km/h) and 130 mph (209 km/h), dangerously close to the stall limit.
In the area above the target the pilots had also to lower to altitudes between 400 ft (122 m) and 800 ft (244 m), often flying well below the quotes of the peaks of the surrounding mountains. If in an emergency, they still had to be able to regain height very quickly in order to safely carry out the airplane . The maneuver was not easy at all, especially for a B-24 Liberator, known for its limited agility.
The average payload to launch was about 6,200 lbs (2,812 kg), plus any agents.
The crews had to be able to promptly recognize ground light signals, prepared ashore with fires or with flashlights and arranged in such a way as to form coded signs and to be clearly visible. The instructions for Italian partisans were to set three ignition lights placed at 330 feet (100 meters) from each other, in a straight line following the direction of the wind. In addition to fixed lights there was a flashing light source (often an Aldis lamp) that continuously transmitted a recognition letter in Morse code , . The letter was the first one from the final confirmation message that had previously been agreed between partisans and Allied commands and which was broadcast by the BBC (British Broadcasting Corporation) a few hours before the mission. In other cases some fixed lights would be arranged to form predetermined letters (often a T, X or L); fixed signaling was ever accompanied by an intermittent code .
Airplanes carrying supplies and traveling at night were very difficult to spot, but they could be easily heard by anyone. Near the dropping zones Northeast of Udine, for example, it often happened that the Germans, the Cossacks and their collaborators, but sometimes also the Slovene partisans of IX Korpus and even local people, turned on fake fires and alternative signals to confuse allied crew and to try to grab the supplies. Due to this, the droppings were sometimes launched far outside the target and the supplies were promptly stolen to their designated recipients , , , .
Supply flights were characterized by very special procedures.
Immediately after their departure by night, aircraft lights were turned on and the weapons could be used. As long as the airplane was flying above the sea, the tail gunner had to take measurements of the drift due to the wind. He did that dropping illuminating flares which fell and floated on the water and observing their trajectory through his specially modified viewfinder; to this aim, the B-24 was equipped with a special tube, mounted under the fuselage. The observed trajectory data were communicated to navigator as he could in this way correct the route, comparing the information found with those provided by weather forecasting ,.
The navigator, who worked in a compartment which was illuminated but overshadowed outwards and towards the rest of the airplane, had to be an expert in Dead Reckoning (DR) and in celestial navigation and had to be very skilled in the use of the sextant , .
Navigation lights were on from the take-off until the aircraft reached a predefined point over the sea. From that moment on the lights were switched off and it was no longer possible to use the flares.
The bomber, uncomfortably lodged in the lower part of the front nose, became then the eye of the entire crew. He had to carefully observe the territory sliding under him and to recognize, as far as possible, mountains, rivers, towns and any other point of reference on the ground that could have been useful for navigation. When the aircraft reached the target, the bomber had also to operate the command to release the containers which were loaded in the bomb bay; in the meantime he had to transmit the launch signal to the waist gunners, who in this special additional task became ‘dispatchers’ as well, to manually drop the bulk packages away at the right time and to relay the signal to any agents, assisting them in their jump .
Once the aircraft had reached the target, the crew carried out the launch in two or three (sometimes four) rounds on the dropping zone, in order to obtain the best possible accuracy and to avoid to disperse the supplies . The practice of multiple passages extended the permanence of the aircraft in the area and it was considered dangerous by allied liaison officers on the ground , both because it endangered the airplane and its crew and because it revealed to the enemy the exact position of the receiving ground patrols.
Absolute radio silence had to be maintained during the entire mission, except in case of emergency. Only after setting the return route, generally at the time of crossing the coast and getting offshore, a short code number was transmitted to indicate the airplane identification number, the time and the outcome of the mission .
Adverse weather conditions were a major cause of failure. Airplanes that departed from bases in southern Italy to targets in the North had to take an average radius of about 500 miles (805 km). The latitude gap was such that they had to go through three different weather bands. The pilots could start experiencing the most favorable conditions in the first two weather zones only to find out that it was impossible to continue when they reached the most northernmost one.
Especially during the 1944-1945 winter, very poor weather conditions had made Italy the most difficult country to supply in the whole MTO (Mediterranean Theatre of Operations).
North Italy, 15 February 1945. T/Sgt. Charles J. Locasto and S/Sgt. John Padgett of the 885th BS attack constraint ropes to packages before an airdrop from a B-24 Liberator during a special mission .
Bad weather was the major source of concern for the crews. In addition to the usual dangerous phenomena such as extreme turbulence and the formation of ice on the aircraft, at night there was the complication that the cloud formations could not be promptly identified and the center of a storm was not easily identifiable. Common night weather effects, moreover, were the electrical phenomena called ‘St. Elmo’s fire’ , which sprayed sparks from the edges of the wings, lit the propellers as pyrotechnic pinwheels and lit up the nose of the airplane as a neon tube .
The duration of a single missions could get even to twelve hours .
Setting of the USAAF special flights was slightly different from the one of the RAF, although the two air forces cooperated closely. The British, in fact, supplied their Halifaxes and Stirlings with the only fuel needed to carry out the planned route and return to base, with emphasis on lightness and agility of their aircrafts. The Americans, on the other hand, preferred to load all the available fuel on their B-24s and B-17s to ensure the longest possible range, that could prove valuable in the event of unforeseen circumstances; this, of course, loaded the bombers and further limited their already modest maneuverability .
North Italy, 15 February 1945. A B-24 Liberator of the 885th BS drops supplies to the partisans behind enemy lines .
Launching and ground receiving techniques used in special missions were initially approximate to the point that often the supplies were lost or they fell into enemy hands, and many agents were captured. Inadequate identification and inaccurate localization of the Dropping Zones were the determining factor in the failure of many operations. Also the lack of technical preparation of reception teams on the ground and their lack of discipline were the cause of mishaps .
North Italy, 15 February 1945. Some just dropped containers and packages fall after the passage of the B-24 .
As an evidence of how the problem of ineffective reception was serious among the partisans, a note from the general command of the CLN (‘Comitato di Liberazione Nazionale’, the Italian National Liberation Committee), CVL (‘Corpo Volontari della Libertà’ or Volunteer for freedom Corps), issued a form letter which reads:
«… the supplies that we receive from the Allies are significantly below our requirements, and, if we seek the causes, we cannot overlook the fact that we do not observe almost any instruction prescribed by them.
[…] it often happens, and this is more serious, that after receiving the supply we do not take care to notify the Allies, so they carefully avoid to intensify launches as we are conversely continuously asking» .
The situation considerably improved when allied liaison officers began to be parachuted behind enemy lines to directly train partisan troops. However, some problems persisted. Thomas Macpherson from his Coolant mission in Friuli writes to Commander Francesco de Gregori (codenamed ‘Bolla’) on 23 January 1945:
«… it is a pity that the drops of the 20th and 21st were not successful. On the 20th the aircraft came early and it turned around from 18,20 to 20,30 without finding the ground. This drop will be repeated again when the weather will be fine, because, among other things, it will bring us some essential radio spares. We hope to recover the most part of the supplies from the drop of the 18th» .
Even after the end of hostilities in Italy, which occurred on 2 May 1945, the special air squadrons continued to receive requests to supply partisan units that were still cut off from other supply channels. Special operations in Italy did actually finish on 7 May 1945 .
 Warren (1947), p. 107.
 MacCloskey (1966), p. 40.
 Lettera circolare (1944), CVL – CNL.
 MacCloskey (1966), p. 40.
 Brown (1987), p. 6.
 Angeli [a cura di] (2002).
 Piffer (2010), p. 136.
 MacPherson, Report on COOLANT mission (1945), p. 57.
 Peterson et al. [ed.] (1963), p. 7.
 MacCloskey (1966), p. 32.
 Collier (2003).
 Peterson et al. [ed.] (1963), p. 8.
 MacCloskey (1966), p. 36.
 MacPherson (1945), p. 58.
 Peterson et al. [ed.] (1963), p. 10.
 Condit (1954), p. 23.
 The U.S. National Archives and Records Administration, Washington, RG 18, E 342 FH, B 100, image #3A-24535.
 Fish (1990), p. 203.
 MacCloskey (1966), p. 39.
 Schwab (1996), p. 46.
 Peterson et al. [ed.] (1963), p. 10.
 The U.S. National Archives and Records Administration, Washington: RG 18, E 342 FH, B 100, image #3A-24536.
 Piffer (2010), p. 96.
 The U.S. National Archives and Records Administration, Washington: RG 18, E 342 FH, B 100, image #3A-24537.
 Lettera circolare (1944), CVL – CNL.
 Macpherson (1945). The original document is written in Italian.
 Warren (1947), p. 112.