The five data blocks every air waybill needs
An air waybill — and the FWB message that represents it digitally — is organised into five logical blocks. Miss any one of them and the airline will issue an FNA rejection before the cargo ever touches the aircraft.
1. Shipper block: the full legal name, address (street, city, country), and contact details of the party handing over the goods. Airlines and customs treat this as the originator of the consignment.
2. Consignee block: the receiving party's name and address at destination. This must be a named person or company — "To Order" or blank is not accepted in FWB/17.
3. Routing block: origin and destination airport codes (e.g., PVG–MXP), the carrier code, and the flight/date. Multi-leg itineraries list each segment in sequence.
4. Goods description block: nature of the goods, number of pieces, gross weight (kg), chargeable weight, volume (if applicable), and any Special Handling Codes (SHC) for dangerous goods or temperature-sensitive cargo.
5. Charges block: whether freight is prepaid (PPD) or collect (CCD), the rate per kg, and any surcharges. Mismatched prepaid/collect declarations are one of the most common FNA triggers.
Calculating the AWB check digit (mod-7 rule)
The AWB number is not just a reference — the 8th and final digit of the serial is a mathematical check digit calculated by the unweighted modulus-7 rule. To compute it, divide the seven-digit serial by 7 and use the remainder, including 0, as the check digit.
Example (the golden reference): serial 1234567 → 1234567 ÷ 7 = 176366 remainder 5 → check digit is 5 → full number 020-12345675. A serial with remainder 0, such as 1234562, ends in check digit 0: 020-12345620.
When you transmit an FWB with the wrong check digit, the airline's system immediately raises an FNA. Use the check-digit calculator at /tools/awb-check-digit to verify or recompute the digit before you build the message.
Building the FWB Cargo-IMP message
Once you have the five data blocks, you map them into the FWB/17 Cargo-IMP format. Each block corresponds to a labelled line set: SHP (shipper), CNE (consignee), RTG (routing), GEN (general information), RCS/DIM/SSR (goods), and CHG (charges).
The most common formatting mistakes that trigger FNA responses are: • Missing or empty CNE line • Charges total that does not balance to the declared rate × weight • Incorrect airport code (IATA 3-letter code required, not ICAO 4-letter) • Country codes that are ISO 2-letter but entered as 3-letter
Paste your draft FWB into the free validator at /fwb-validator and AWB Studio will flag each issue in plain English before you send it to the airline.
What triggers an FNA response
An FNA (Freight Not Accepted) is the airline's machine-generated rejection of your FWB. Common triggers include an invalid AWB check digit, a missing consignee block, an unbalanced charges declaration, and unsupported special-handling codes. Airlines return an FNA with a coded reason — but the code alone rarely tells you where exactly the message broke.
AWB Studio's validator translates those codes into forwarder-plain language: "Your CNE block is missing — add the consignee name and address" rather than "FNA: CNE-01." Fix the message, revalidate, and retransmit — typically within minutes.