Pan Am. TWA. Eastern. Braniff.
Their planes were once familiar sights at airports across the country and even around the globe. They helped define air travel for decades.
Today they exist either in name only or in collectors' memorabilia.
The U.S. airline industry was once filled with dozens of carriers whose planes crisscrossed the nation and flew over oceans, but consolidation has culled the flock to just a handful of companies.
The pending merger of American Airlines and US Airways will leave four big airlines that will dominate the U.S. travel market -- the post-merger American, United, Delta and Southwest -- and a smattering of smaller rivals.
Even if their merger is approved this year, American and US Airways will continue to operate as separate airlines for at least several months. But eventually, executives say, the US Airways name will disappear.
The same will happen over the next few years with AirTran Airways, which was bought by Southwest in 2011. AirTran planes will be repainted in Southwest's logo and colors.
Here are some famous airlines that failed or were bought out by rivals:
• Pan Am. It started with mail delivery in the 1920s and grew into a giant of international passenger service. It started operating jets in 1958, was a symbol of luxury travel in the 1960s. Years of financial trouble and rising competition took their toll. Pan Am sold off valuable assets including its Pacific routes and New York-to-London route. It failed in 1991, although other companies have reused the name since.
• TWA. Trans World Airways was a major domestic player and competed with Pan Am on international routes. Known for leading technology, TWA used pressurized planes and was an early proponent of jets. It struggled with high fuel prices in the 1970s and -- after deregulation of the airlines -- competition from low-fare carriers in the 1980s. Corporate raider Carl Icahn bought it and sold many routes. American Airlines bought TWA out of bankruptcy in 2001 and retired the name.
• Braniff. It built a powerful hub airport operation in Dallas and roamed across the middle of the country and even as far as Hawaii with a fleet of colorfully painted planes. Braniff was squeezed by competition from American and upstart Southwest Airlines, however, and it shut down in 1982. Jay Pritzker, whose family owned the Hyatt Hotels chain, resurrected an airline that came to be known in the industry as Braniff II, but it too failed.
• Eastern Air Lines. Famed aviator Eddie Rickenbacker bought Eastern, which had been pieced together from several predecessors, in 1938. It built a successful network along the East Coast and launched low-fare shuttle flights from New York to Washington and Boston. It was hurt by competition from Delta and People Express and was beset by labor-management tension, including strikes, under Frank Lorenzo. It failed in 1991.
• People Express. One of the first airlines to take advantage of deregulation. People Express was modeled after a British low-fare airline, and started flying in 1981 in Newark, N.J. It grew quickly -- maybe too quickly. Burdened with debt, it was merged with Continental in 1986. A new carrier began using the name last year.
• Northwest Airlines. The Minnesota-based carrier was noted for its strong routes across the Pacific to Japan. In 1993, it formed a partnership called a code-sharing agreement with Dutch carrier KLM, and that deal became the forerunner of modern airline alliances. Delta Air Lines bought Northwest in 2008, making Delta the biggest airline in the world -- at least until 2010.
• Continental Airlines. It began as Varney Speed Lines in the 1930s and eventually grew to offer transcontinental and international service. Lorenzo's Texas International bought the airline and combined it with others including Frontier and New York Air. It went through two bankruptcies but was brought back from the brink by CEO Gordon Bethune. It combined with United Airlines in 2010, allowing United to surpass Delta as the world's biggest airline. The final Continental flight landed in March 2012.