Local service carriers, or local service airlines, originally known as feeder carriers or feeder airlines, were a category of US domestic airline created/regulated by the Civil Aeronautics Board (CAB), the now-defunct federal agency that tightly regulated the US airline industry 1938–1978. Initially 23 such airlines were certificated from 1943 to 1949 to serve smaller US domestic markets unserved/poorly served by existing domestic carriers, the trunk carriers, which flew the main, or trunk, routes. However, not all of these started operation and some that did later had their certificates withdrawn. One other carrier was certificated in 1950 as a replacement. "Feeder airline" alludes to another purpose, that such airlines would feed passengers to trunk carriers. It was expected that a significant number of passenger itineraries would involve a connection between a local service carrier and a trunk carrier.
Local service carriers ultimately became substantial carriers in their own right, all such carriers flew jet aircraft by the end of the regulated era (1978). Over time, local service carriers began to compete more directly with trunk carriers. But a clear distinction, visible in financial and operating data, continued to exist between the two types of domestic carriers through the end of the regulated era, reflecting a difference in how the CAB regulated the two types of carriers. In particular, in contrast to trunk carriers, local service airlines received government subsidies throughout the regulated era. But after US airline deregulation in 1979, the distinction between trunk and local service carriers vanished.