Regional Service

United, American, Eastern, and TWA dominated the major transcontinental routes, while smaller airlines served specific areas of the country.

Beyond the "big four" major carriers, a few other large airlines-Delta, Braniff, Western, Continental, and Northwest-provided service to particular regions. Federal regulators limited competition between them by preventing their territories from overlapping, except on heavily traveled routes.

After 1955 a new category of smaller airlines providing local service gained official recognition. These so-called regional airlines brought airline service to hundreds of small cities.

Regional airlines operated the same large aircraft as the "big four" airlines. But for short- to medium-length routes, they used smaller aircraft as well.

After World War II, the major airlines began looking for a replacement for the venerable DC-3. American Airlines led the way by cooperating in the development of the Convair 240. The Martin 2-0-2, which first flew with Northwest, was designed to compete with the 240.

Improved models followed and helped fill the need for smaller airliners flying shorter routes.

The pressurized, 40-seat Convair 240 brought a new level of comfort and productivity to American Airlines' secondary routes. The 240 and its stretched 340 and 440 versions proved popular among major, secondary, and local-service airlines.

The Martin 2-0-2 debuted in 1947. However, serious technical flaws in the wing structure limited its usefulness. Redesigned with an improved wing and a pressurized fuselage, the Martin 4-0-4 served with distinction with TWA, Eastern, and other airlines.