Contracting with outside companies is an effective, cost-efficient step for many industries. During the nineteenth century, contracts with stagecoach, steamship, and railway lines provided the Post Office Department with the ability to select the best and fastest way to move the mail. In return, the Post Office Department was able to expand mail service rapidly as demand grew. On the other hand, contracts with the Post Office Department supplied crucial financial subsidies for these companies. In the twentieth century, for instance, the airline industry received start-up funding through airmail service contracts. Today, the scope of the U.S. Postal Service’s mission is so vast that not even the largest civilian working force, using the largest civilian transportation system, can handle it. Contractors continue to allow for flexibility, economy, and efficiency in certain services that the U.S. Postal Service could not fulfill alone.