A primary goal of the National Drug Control Strategy is to reduce the amount of illegal drugs entering the United States. South America is a major source of drugs, particularly cocaine, shipped through the transit zone to the United States. In 2000, ONDCP estimated that 31 percent of cocaine shipped from South America to the United States transited the Caribbean Corridor, and 66 percent came through the Mexico-Central America Corridor (which includes the Eastern Pacific). The remaining 3 percent went directly from South America to the continental United States (see fig. 1). According to the National Drug Control Strategy 2000 Annual Report, drug interdiction in the transit zone is intended to disrupt the flow of drugs, increase risks to traffickers, force traffickers to use less efficient routes and methods of delivery, and prevent significant quantities of drugs from reaching the United States. Drug interdiction operations may also produce information that can be used by domestic law enforcement agencies against trafficking organizations. According to the 1999 National Interdiction Command and Control Plan, a completed drug interdiction normally consists of six phases, some of which may occur simultaneously. (1) Provision of intelligence information to drug interdiction agencies indicating that a drug-smuggling activity is planned or underway. (2) Initial detection of a potential smuggling aircraft or vessel. (3) Monitoring, which consists of tracking a target aircraft or vessel (maintaining information on its position, course, and speed) and moving to intercept it. (4) Identifying drug-smuggling traffic from legitimate traffic. (5) Handoff, or shifting of primary responsibility between forces, such as from DOD to the Coast Guard. (6) Apprehending (detaining, arresting, or seizing) suspects, drugs, or vehicles or causing the suspects to jettison their drugs or to turn back from their mission. In this report, we use the term “drug interdiction” to refer to activities in any or all of these six phases. In a hypothetical example, drug interdiction agencies receive intelligence that a drug-smuggling aircraft will be leaving South America en route to the United States in the next few days. A DOD radar facility subsequently detects a small, low-flying plane on a known trafficking route. Alerted by this information and other intelligence, a military aircraft uses its radar system to track the plane. A Customs aircraft then approaches the suspect plane to make a visual identification. The Customs pilot observes the suspect plane dropping what appears to be a load of drugs to a waiting smuggling vessel in the waters below. The location of the vessel is given to the Coast Guard so that it can apprehend the drug-smuggling suspects and seize the drugs. The plane is tracked by the Customs pilot, and foreign law enforcement forces are alerted so that they can apprehend the drug- smuggling suspects when the plane lands at a foreign airfield. The interdiction roles of DOD, the Coast Guard, and Customs overlap regarding the types of activities they perform and the geographic areas they cover. Because of this, the agencies must cooperate and work together in order for interdiction to be successful. Five coordinating organizations also guide and support their activities. DOD serves as the lead federal agency for detecting and monitoring air and maritime transit of illegal drugs into the United States. DOD uses equipment such as Navy ships and aircraft, Air Force aircraft, and radar for this purpose (see fig. 2). The Coast Guard and Customs also provide aircraft and ships for detection and monitoring, but DOD coordinates and integrates their efforts. By statute, DOD personnel may not directly participate in a search, seizure, arrest, or other similar activity, unless authorized by law. As a result, DOD relies on U.S. or foreign law enforcement agencies to exercise civilian law enforcement powers to carry out that part of the interdiction effort. Within the transit zone, the Coast Guard is the lead agency for the apprehension of maritime drug traffickers. In addition, Coast Guard law enforcement detachments are required by statute to travel on board designated Navy ships for drug interdiction missions to perform law enforcement functions. During boarding operations, the Navy ships come under the operational control of the Coast Guard detachments. These detachments perform the actual search and seizure of a suspect vessel, and make any arrests, since the U.S. military is prohibited from doing so. (See fig. 3 for examples of Coast Guard assets.) Within the transit zone, Customs is co-lead with the Coast Guard for the apprehension of drug trafficking aircraft. The agency also assists the Coast Guard with apprehension of maritime drug traffickers. For example, a Customs aircraft equipped with surface search radar can detect and track a maritime vessel, then work with Customs boats and Coast Guard ships to apprehend the suspect drug traffickers. (See fig. 4 for examples of Customs assets.) Coordinating organizations help guide and support the three agencies’ drug interdiction efforts in the transit zone. Their transit zone roles are briefly discussed in table 1. Representatives from DOD, the Coast Guard, and Customs advise the U.S. Interdiction Coordinator, and staff JIATF- East, JIATF-West, and AMICC. Appendix II contains more detailed information on these organizations. DOD, the Coast Guard, and Customs do not track data on funds obligated and assets used specifically for transit zone drug interdiction. For the purposes of this review, we asked agency officials to attempt to isolate funds they obligated and assets they used for drug interdiction in the transit zone. DOD, the Coast Guard, and Customs attempted to produce such estimates, but because of substantial differences among the agencies’ methods and other limitations, these estimates were not reliable, and will not be presented in this report. specifically for transit zone drug interdiction. The three agencies provided us with estimates of those funds, but these estimates had a number of limitations. In the case of DOD, the agency could not isolate its funds obligated for transit zone drug interdiction for several reasons. First, DOD could not always distinguish funds obligated for detection and monitoring from those used for noninterdiction counterdrug activities. DOD provided us with a list of funds obligated for individual DOD programsfor fiscal years 1998 through 2000, broken out by country or geographic area and by type of counterdrug activity (such as detection and monitoring). However, there were instances where the individual funded program had multiple purposes. For example, funds DOD obligated to several programs in the Caribbean were used for both detection and monitoring and for noninterdiction counterdrug activities. Including such cases resulted in an overestimate of the funds obligated exclusively for detection and monitoring, and thus for transit zone drug interdiction. Second, the funds obligated did not include active-duty personnel costs,resulting in an underestimate of total funds obligated for transit zone drug interdiction. Third, funds obligated for detection and monitoring in the Eastern Pacific area could not be included in our analysis because DOD did not track funds obligated specifically for that area, resulting in an underestimate of total funds obligated for transit zone drug interdiction. As with DOD, the Coast Guard could not identify funds obligated for transit zone drug interdiction. The agency’s estimate did not cover the entire time period requested and was not specific to the transit zone. The Coast Guard provided us with estimates of funds obligated for fiscal years 1999 and 2000. According to Coast Guard budget officials, data were unavailable for 1998 because ONDCP did not require agencies to report their funds obligated for drug interdiction until 1999. In addition, the Coast Guard’s estimates of funds it obligated for drug interdiction were based on the hours spent on drug interdiction missions combined with a cost factor. Because the agency’s tracking system does not distinguish hours spent in the transit zone from hours spent in U.S. territorial waters, the data the Coast Guard provided to us included funds obligated for drug interdiction activities in both areas. Likewise, Customs could not isolate funds obligated for transit zone drug interdiction, in this case resulting in an underestimate of these funds. Three factors contributed to this underestimation. First, the data were not representative of all of Customs’ transit zone air interdiction efforts. Customs’ estimates of funds it obligated for transit zone interdiction were based on the recorded hours each aircraft spent on interdiction activities in the transit zone, multiplied by the average hourly operating cost for that type of aircraft. Customs provided data for specific flights made during fiscal years 1998 through 2000 where pilots indicated that their mission was in the transit zone. However, pilots were not required to record that information in Customs’ data system. For example, a Customs aircraft could take off from Miami and fly to a drug interdiction mission in the transit zone. Unless the pilot specified the location of the plane, those hours would be logged to the Miami Air Branch rather than to any specific geographic area. Customs was not able to estimate, for those flights in which the geographic area had not been recorded, the amount of time those pilots spent in the transit zone. Second, as with DOD, the Customs data did not include personnel costs because Customs does not track personnel costs by mission type. Third, Customs did not provide data on funds obligated for its marine unit’s transit zone drug interdiction activities because, according to a Customs official, marine unit data were unreliable prior to October 2000. The marine unit did not have a centralized reporting system before its merger with the air unit in 1999, and the agency’s data collection system was not modified to incorporate data from its marine assets until October 2000. Agency budget officials told us that although they do not track funds obligated for transit zone drug interdiction, they track funds obligated for drug interdiction in other ways that are more consistent with their responsibilities in the transit zone and elsewhere.