Federal law requires every shipment loaded onto a passenger aircraft in the United States to be screened for threats before departure, and the air cargo screening methods approved for that job are X-ray imaging, explosive detection systems, explosive trace detection, TSA-certified canine teams, electronic metal detection, and physical search paired with manifest verification. Each method is written into 49 USC 44901, and each is suited to different cargo types, densities, and volumes.1Office of the Law Revision Counsel. 49 USC 44901 – Screening Passengers and Property The governing standard is that cargo carried on a passenger plane must receive a level of security comparable to what a checked suitcase gets.
The Standard Behind Every Method
The Implementing Recommendations of the 9/11 Commission Act of 2007 required a system capable of screening 100 percent of cargo transported on passenger aircraft, with an interim target of 50 percent by February 2009 and full compliance by August 2010.2Federal Register. Air Cargo Screening The statute defines screening as a physical examination or non-intrusive assessment of whether cargo poses a threat, and it lists the approved methods below. Anyone tendering cargo for air transport must consent to a search or the shipment is refused.3Transportation Security Administration. Cargo Programs
One boundary matters up front. Reviewing shipping documents or confirming a shipper’s identity, including through the Known Shipper Management System, does not count as screening on its own.1Office of the Law Revision Counsel. 49 USC 44901 – Screening Passengers and Property Known-shipper cargo still has to go through one of the physical or technological methods described below.
Physical Search With Manifest Verification
Physical search is the most basic approved method and the fallback for cargo that imaging or trace detection cannot handle well because of density, composition, or unusual packaging. Inspectors open individual packages and check for signs of tampering such as re-taped seams, unexpected weight distributions, or odors that might indicate chemical agents. They compare what they find against the shipping manifest to confirm the contents match.
Because a physical search only screens what is on the table at that moment, the shipment must then be protected from tampering. Screened cargo travels with a screened-cargo indicator and paperwork such as an air waybill, showing the date of departure or pickup, piece count, weight, and signatures of authorized security personnel.4Transportation Security Administration. Air Cargo Screening Final Rule If chain of custody is broken at any point before loading, the cargo has to be re-screened.
X-Ray Imaging
X-ray systems pass cargo through a tunnel and produce digital images that a trained operator evaluates on screen. TSA classifies imaging devices by the number of views they capture (single, dual, or multi-view) and whether they can discriminate between material types.5Transportation Security Administration. Non-SSI Air Cargo Screening Technology List Machines with material-discrimination capability use color coding so the operator can distinguish organic from inorganic materials. Dense objects that X-rays cannot penetrate show up as opaque regions, and those items get flagged for secondary screening by another method.
Devices are also classified by physical capacity. Small-aperture units handle items about the size of a large suitcase and up to roughly 220 pounds. Medium-aperture machines take freight up to about 2,200 pounds. Large-aperture systems accept anything bigger, including full cargo pallets. Every X-ray device used at a screening facility has to appear on TSA’s Air Cargo Screening Technology List. Devices placed on the list in conditional-approval status have up to 36 months to pass field testing; those that fail are removed.5Transportation Security Administration. Non-SSI Air Cargo Screening Technology List
Explosive Detection Systems
Explosive detection systems (EDS) are a step above standard X-ray. They use computed tomography and automated algorithms to build three-dimensional models of the items inside a container, then analyze mass, density, and composition to flag anything matching the profile of known explosive materials.5Transportation Security Administration. Non-SSI Air Cargo Screening Technology List Because the detection is automated, EDS reduces reliance on an operator’s visual judgment. When the machine alarms, the operator reviews the CT image and decides whether a physical follow-up is needed. EDS units are listed as their own category on the Air Cargo Screening Technology List, separate from standard visual-image X-ray devices.
Explosive Trace Detection
Explosive trace detection (ETD) looks for microscopic chemical residues rather than physical shapes. An inspector swabs the handles, seams, and openings of a package, then inserts the swab into a detection unit. The machine heats the sample to vaporize collected particles and uses ion mobility spectrometry to measure how fast the resulting ions travel through a drift chamber. Each explosive compound produces a distinct signature, letting the system detect nanogram-level quantities.
ETD works well for shipments with complex internal structures where imaging alone may not reveal the chemical nature of the contents. Screeners collect swabs from specific locations on each piece of cargo to achieve the 100 percent screening requirement.4Transportation Security Administration. Air Cargo Screening Final Rule Equipment must be maintained and calibrated according to the procedures in the facility’s TSA-approved security program, and calibration and test logs have to be kept in order.
Certified Explosive Detection Canines
Trained dogs are one of the fastest tools available in a high-volume cargo environment. TSA’s Third-Party Canine-Cargo (3PK9-C) program allows private companies to field explosive-detection teams that are certified to TSA standards by an approved non-governmental evaluator.3Transportation Security Administration. Cargo Programs Because canines detect airborne scent particles, they can clear large pallets and consolidated shipments without breaking down individual packages, which is where imaging machines create bottlenecks.
Certification events are conducted by evaluators employed by TSA-approved certifiers, following procedures in the 3PK9-C Security Program and Order. The specifics of that program are classified as sensitive security information and are not publicly available.6Federal Register. Announcement of Approved Third-Party Canine-Cargo Certifiers and Start of Certification Events Handlers complete security threat assessments, and both handler and canine have to demonstrate proficiency in identifying threat scent profiles in an operational warehouse setting.
Electronic Metal Detection
Electronic metal detection has a narrower role. It fits cargo made mostly of non-metallic materials such as textiles, paper products, or plastics, where a hidden metallic threat would be the main concern. Systems use electromagnetic induction: when something metallic passes through the field, the resulting disturbance triggers an alarm. Facilities may use industrial walk-through magnetometers or handheld wand-style detectors depending on the size and type of shipment. This is a targeted screen, not a general-purpose tool.
Chain of Custody After Screening
A screening result only stays valid if the cargo is protected afterward. Facilities have to maintain chain of custody through tamper-evident technologies and documentation until the shipment is handed off to an aircraft operator, another certified facility, or an indirect air carrier. Any break means the cargo has to be screened again.4Transportation Security Administration. Air Cargo Screening Final Rule
Recordkeeping runs in parallel. Training records for every individual who performs screening must be retained for 180 days after that person leaves the facility or stops acting as its agent. Other operational records generally have to be kept until the facility’s next re-certification.7eCFR. 49 CFR 1549.105 – Recordkeeping
Choosing a Method
No single method covers every shipment well. Standard X-ray works for most general freight but struggles with dense loads. EDS handles suspect items with automated CT analysis. ETD catches chemical residues that imaging misses. Canines move volume without unpacking pallets. Metal detection covers commodity cargo where a metallic threat is the specific worry. Physical search backstops anything the technology cannot resolve. In practice, a screening facility combines several of these so that the method fits the cargo rather than the other way around, and any item that fails one screen moves to a second before it goes anywhere near an aircraft.