支线飞机是指设计座位数量约在35至100之间的小型民航飞机，常见有50人和80人两种等级，后来逐渐出现增至120人左右的加长款式。其典型特征即承担大型航线以外局部短距离、小城镇、高山地区、离岸岛屿之间商业运载，也可用于军事，如承担运载兵力、资源补给之用。

生产制造方面，从前的义法ATR系列、瑞典绅宝集团生产的螺桨支线飞机，到小有名气的加拿大的庞巴迪航空（Bombardier）和巴西航空工业（Embraer）的喷射产品都是常见的支线飞机主要制造商，近年来除了两大厂商开始更新其机型之外，传统航空大国苏联解体后，乌克兰也重新推出了安托诺夫An-148，同时俄罗斯生产的现代化SSJ-100、开发中的图-334等等使支线飞机逐渐进入了新时代，而新崛起的中国商飞ARJ21、日本三菱支线喷射机则是未来潜在的竞争者。

A regional airliner or a feederliner is a small airliner that is designed to fly up to 100 passengers on short-haul flights, usually feeding larger carriers' airline hubs from small markets. This class of airliners are typically flown by the regional airlines that are either contracted by or subsidiaries of the larger airlines. Regional airliners are used for short trips between smaller towns or from a larger city to a smaller city. Feederliner, commuter, and local service are all alternative terms for the same class of flight operations.