The test marks a key step in Qantas's Project Sunrise, which aims to launch the world's longest commercial passenger services and reshape long-haul travel by eliminating stopovers between Australia and Europe.
The specially adapted A350-1000ULR airliner is due to debut with the Australian carrier's non-stop Sydney-London route from 2027.
Airbus has been conducting a two-month test campaign on the aircraft since June.
Airbus said the aircraft, which boasts a specially designed extra fuel tank, remained in the air for 24 hours and 24 minutes, covering 23,075 km without stopping, before landing at the plane's factory in Toulouse, France, on Tuesday.
Flight-tracking provider Flightradar24 said the trip was the second-most-tracked flight ever on its channels - behind a 2024 flight carrying Queen Elizabeth II's coffin - with more than 3.6 million people following its progress northwards via Canada.
In 2005, a Boeing 777-200LR Worldliner flew 21,601.7km from Hong Kong to London in 22 hours and 42 minutes.
Qantas has ordered 12 modified A350-1000ULR aircraft, designed to connect Australia's east coast with London and New York in about 20 hours.
The services aim to turn what was once a five-day journey on the "Kangaroo Route" to London into a single flight lasting 19 to 21 hours, depending on routing and winds.
The first aircraft, which carries 20,000 litres of fuel and can seat 238 passengers, is due for delivery in April 2027.
Qantas expects to operate daily non-stop flights between Sydney and London from October 2027.
