Using COS on air freight documents
The three-letter IATA code COS is what goes on an air waybill, a booking and a flight schedule for City of Colorado Springs Municipal Airport; the four-letter ICAO code KCOS identifies the same airport in flight plans and air-traffic control and does not appear on cargo paperwork. A forwarder quotes airport-to-airport between two IATA codes unless the booking is door-to-door, so the code fixes where the rate applies.
The Census Schedule D list does not name City of Colorado Springs Municipal Airport as a separate airport port of entry, so this page assigns no CBP code. Customs ports are often listed by city or district; the CBP Schedule D directory lists every one.