Available seat miles is a measure of capacity calculated as the number of seats available multiplied by the distance traveled.

Capacity is a measure of total seats operated by an airline or multiple airlines between two nonstop segments.

Domestic destinations served is the number of airports served with nonstop flights within the United States.

A passenger boarding a flight at a given airport is an enplanement. This includes passengers boarding an aircraft from a previous (connecting) flight.

In the United States in 2021, there were 11 air carriers that operated flights to 110 small communities supported by the Essential Air Service (EAS) program. These carriers tend to operate small aircraft. Of the 110 EAS communities, half received flights with 50-seat aircraft, and another 44 received flights with 8- or 9-seat aircraft. Most of that service was operation of flights to large hub airports that also served as major airline hubs (e.g., Hartsfield–Jackson International Airport, Los Angeles International Airport, O’Hare International Airport, and Minneapolis–Saint Paul International Airport). The EAS program provides a vital link for those communities to the national air system.

Frequency is the number of departures, commonly measured as the average number per day. This measure typically reflects scheduled operations, as opposed to operations performed. (The two may differ for multiple reasons, but most commonly because of cancellations due to weather or other airline operational issues.)

International destinations served is the number of airports served with nonstop flights outside of the United States.

Passengers fly between a point of origin (O) and a point of destination (D). The “O&D record or routing” reflects the full itinerary that a passenger flies and may contain one or more segments or flights. O&D routings with one segment are called nonstop. The volume of O&D traffic in a city-pair market is a measure of the total demand for air travel between the two locations.

Passengers per day each way (PDEW) is a common demand measure of O&D passengers in the form of one-way directional passengers per day.

Regional aircraft most often refers to an aircraft with fewer than 76 seats.

Revenue passenger miles (RPMs) is a measure of traffic demand calculated as the number of revenue-paying passengers carried multiplied by the distance traveled.

Because airlines may launch or end operations at different times within a year and because some airlines may operate only occasional (or seasonal) flights, to sustain or facilitate economic activity between two points, some minimum number of flights (departures) is often set as defining “service.” The analysis presented here uses 50 flights per year.

A related consideration of air service is whether flights are offered by legacy network carriers, low-cost carriers, or ultra-low-cost carriers. (see below). The types of carriers providing service have implications for the number of domestic and international destinations that can be readily served.

Airports and their cargo communities are adopting new technologies to increase efficiencies in air cargo processes and supply chains. Cargo community systems (CCSs) are promoted as a way to solve congestion issues around airports, especially on the landside. CCSs can help with trucking and freight forwarding to reduce on-airport wait times; increase efficiency and accuracy of information and communications; increase productivity, throughput, and utilization of resources; and increase capacity within existing cargo-related facilities and infrastructure.

Most CCSs involve usage by a number of cargo stakeholders (shippers, airlines, ground handlers, freight forwarders, truckers, etc.) of a common technology platform to exchange information relevant to shipment status and readiness for handling by these parties.

At this time, CCSs are most appropriate and applicable to larger international gateway airports where there are more stakeholders involved in international shipments and the process is complex.

Air exports are the total physical movement of merchandise out of the United States to foreign countries by air, recorded by weight and value.

Air freight is property, other than express freight and passenger baggage, being transported by air.

Air imports are the total physical movement of merchandise into the United States from foreign countries by air, recorded by weight and value.

An all-cargo carrier is an air carrier operating only freighter aircraft exclusively for the purpose of transporting cargo.

The type of products that are shipped, which are categorized using the harmonized categorization system to varying levels of specificity.

E-commerce (electronic commerce) is defined as the commercial transaction of money, funds, and data and buying and selling of goods, products, or services via the internet.

Express freight is property, other than passenger baggage, for which a premium over standard freight prices is charged for faster delivery.

An express freight carrier is a carrier handling all aspects of the supply chain for freight, including pre-shipment, shipment, and post-shipment transportation processes (e.g., FedEx, UPS, and DHL).

Tons shipped is the total weight of an entire shipment reported in pounds; pounds are then converted to short-tons (2,000 pounds) and displayed in thousands.

Value of shipment is the dollar value of the entire shipment, excluding taxes or fees, expressed in millions of dollars.