Like most local service airlines Southern flew only Douglas DC-3s for the first few years. In 1961 they began adding 22 40-passenger secondhand Martin 4-0-4s acquired from Eastern Air Lines, newer aircraft that were pressurised and had a rear ventral stairway. The last DC-3 was retired in 1967.
Community Q&A. An operating system (OS) is software that manages the interaction between hardware resources and the programs or applications you use on a computer. Most PCs have a version of the Windows operating system on them but Macintosh, Linux and UNIX are other popular operating systems.
Also called laptop. A set of programs that manages and coordinates all the activities in a computer. Main operating systems for personal computers are Windows, Apple, Linux, and Chrome. Mobile operating systems also depend on the developer, such as Android, Windows Phone, Chrome, and Apple iOS. Also called platform.