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.
disk operating system, DOS - an operating system that is on a disk. UNIX, UNIX operating system, UNIX system - trademark for a powerful operating system. executive program, supervisory program, supervisor - a program that controls the execution of other programs.