the Boeing 377 Stratocruiser

The Boeing 377, often called the Stratocruiser, first flew on 8 July 1947.  It was developed from the C-97 Stratofreighter, a military derivative of the B-29 Superfortress used for troop transport.
It had four piston propeller engines with surprisingly low fuel consumption for the era and was able to cruise at about 32,000 feet. It also had a pressurized cabin, a relatively new feature of that time. At cruising altitude the cabin altitude was 5,500 ft (1,700 m), not much more than the standard 5,000 ft today.  A total of 56 were built, the main users being Pan Am, BOAC and Northwest. The airlines were able to make transoceanic flights easier and faster with the new aircraft, which enabled easier international travel, but the planes did not have great reliability and performance.

They had two decks: the upper deck was for economy class customers, while the lower was a VIP lounge and bar. Passengers could walk down and get a drink on the long flights, once the plane leveled off at cruising altitude. Most Stratocruisers had economy seats on both decks.

When jet airliners were introduced in the late 1950s, propeller planes such as the Stratocruiser became uncompetitive for major airlines, and many were sold off to feeder lines. Others scrapped, while some were converted by Aero Spacelines to Guppys, which were versions of the Stratocruiser with an enlarged fuselage and turboprops. One version, the Super Guppy, was used by Airbus to transport aircraft parts between factories, since replaced with Airbus Belugas.