Airline is a company which operates aero planes in commercial service, carrying passengers or freight. Some airlines are very large, such as British Airways or Qantas; others may be very small, with only one aircraft. Some, for example, purchase their aircraft, customizing them to offer special services such as reclining beds for passengers. These companies staff their planes with pilots and cabin crew who train to work specifically for them. Others lease their aircraft and staff from other companies.
In either case, the company is heavily supported by a large ground staff which includes reservation agents, cleaners, caterers, and loaders, among many others. Freight carriers also typically follow a regular schedule through a myriad of set routes that are designed to efficiently move packages from one place to another.
It may supplement its aircraft with delivery trucks, or it may only offer bulk transit from one airport to another, with customers responsible for moving the freight to and from the airport. The cabins of these aircraft are also laid out very differently than passenger aircraft, allowing staff to pack the planes with freight and packages. Sending people and goods by air is a rapid and efficient way to get them from place to place.