In economics, a virtual airline is an airline that has outsourced as many possible operational and business functions as it can, but still maintains effective control of its core business. Such an airline focuses on operating a network of air services, and outsourcing non-core activities to other organizations. Contracting out services within the aviation industry has reportedly become so common that many carriers could be classed as having features of a virtual airline, although it is arguable whether any current carriers meet a strict definition of the term.

A mainline flight is a flight operated by an airline's main operating unit, rather than by regional alliances, regional code-shares, regional subsidiaries, or wholly owned subsidiaries offering low-cost operations. Mainline carriers typically operate between hub airports within their network and on international or long-haul services, using narrow-body and wide-body aircraft. This is in contrast to regional airlines, providing feeder services to hub airports operating smaller turboprop or regional jet aircraft, or low-cost carrier subsidiaries serving leisure markets.