A chapter of aviation history is closing this year, as commercial U.S. airlines bid farewell to the Boeing 747, the jumbo jet that made air travel affordable for millions of people around the globe because it could fit hundreds of passengers inside.

The double-decker plane with the humped fuselage is one of the world's most recognizable planes. But after flying the four-engine, fuel-guzzling plane for decades, Delta Air Lines and United Airlines are retiring the so-called Queen of the Skies in favor of sleeker, more fuel-efficient models that are cheaper to operate. The planes are used frequently for cargo, which was part of the inspiration for the plane's design: Some models were given a hinged nose to allow for easy loading of goods.

In a sign of how efficient modern planes have become, Southwest Airlines last month announced it will offer service to Hawaii, and new, single-aisle Boeing 737s will likely do the job.

Delta Air Lines marked the retirement of its Boeing 747s this week with a six-city tour, the last U.S. airline to retire the jumbo jet.

United pulled out all the stops for a farewell flight last month. Its first 747 took off from San Francisco and flew to Honolulu in 1970. It retraced that route for the final passenger flight Tuesday, complete with a crew dressed in 1970s uniforms. Smoking was not permitted, however.

The plane will live on as a workhorse cargo jet, flown by UPS and others.

Here's a look at the Boeing 747, and how it changed the world from its introduction nearly five decades ago: