(CNN) — While flying is still considered a quintessentially modern way to travel, many airlines have now clocked up decades of history.
And one is taking its heritage very seriously.
German airline Lufthansa has been busy restoring classic examples of its former fleet for displays and experience flights.
It's just brought back into service the oldest aircraft in its fleet, a Junkers Ju-52, and is set to recommission a Lockheed L-1649A Starliner from 1957.
Lufthansa has also been actively involved in the recovery of a 1970s Boeing 737 -- known as Landshut -- with an infamous past as the target for a hijacking.
So what are the stories behind these illustrious old flying machines?
'Auntie Ju' Ju-52 (D-AQUI)
The Ju-52 D-AQUI has been fully restored with many parts manufactured from scratch.
Deutsche Lufthansa Berlin-Stiftung
Before and after World War II, the Junkers Ju-52 (also known as "Tante Ju" or "Auntie Ju") was the workhorse of many airlines and air forces around the world.
While thousands were built, only a handful are still operational and in flying condition. One of them is D-AQUI, which has been in Lufthansa's fleet since 1984.
This particular aircraft has come full circle. It started its operational life in 1936 with Luft Hansa, the pre-war German airline that preceded the modern Lufthansa (although there is no legal continuity between the two entities).
It was then transferred to a Norwegian airline and, after the German invasion of Norway, spent the war in Scandinavia fulfilling transport duties. In 1955 it was retired from commercial service in Norway, disassembled and transported by sea to Ecuador.
After several years of service in the Amazon basin, it was discovered and purchased by an American citizen, who took it to the United States and subsequently sold it to "The Six Million Dollar Man" writer Martin Caidin.
In 1984 it was bought by Lufthansa to mark its 60th anniversary. The Ju-52 was flown back to Europe, making 16 stops along the way.
Once in Germany it was thoroughly restored and put back into service on panoramic flights.
The aircraft, which sports the Luft Hansa 1936 historical livery, has a packed schedule during summer months. Between May and October it's usually booked up, attending air shows and carrying passengers on a unique flying experience around Germany and Austria.
"It is not unusual to have elderly people, who flew on Ju-52 when they were very young, take their grandchildren on board," explains Wolfgang Weber, a Lufthansa spokesperson.
The Ju-52 spends winters at Lufthansa Technik facilities in Hamburg, where it's subject to intense maintenance work. Taking care of such an old aircraft represents a challenge for the maintenance crews. Parts and spares are hard to come by and very often have to be manufactured from scratch.
Lockheed L-1649A Super Constellation
Lufthansa is rebuilding a Super Constellation similar to this one from 1954.
Keystone/Hulton Archive/Getty Images
The sleek, stylized fuselage and its easily recognizable triple tail make the Lockheed Constellation series one of the most iconic airliners of all times.
Sadly for its numerous admirers, this beautiful aircraft became obsolete shortly after it was launched, as faster jet airliners came to the market.
Lufthansa was one of the handful of airlines that operated the L-1649A -- dubbed the Super Star-- first for passenger services and, from 1960, as a cargo aircraft.
When three of the type, belonging to the same owner, were put up for sale in the United States in 2008, Lufthansa snapped them up at an auction.
"When we first bought the aircraft we thought it was a nice opportunity to recover part of our heritage," explains Weber. "We thought it would be just a matter of months, that we would send some of our technicians, make the necessary repairs and fly them back to Europe. But it turns out they required a lot more work than that."
So much work that Lufthansa even built a new hangar at Auburn-Lewiston airport, in the middle of rural Maine, where two of the aircraft had been based for years. The third aircraft was based in Florida.
"This is not just repair work. We are, in fact, rebuilding these aircraft," adds Weber.
The Boeing 737 named Landshut was flown back from Brazil to Germany inside a giant cargo aircraft.
Karl-Josef Hildenbrand/AFP/Getty Images
Two of the aircraft have been used to provide parts and spares for the only one that will be made airworthy -- the Star of the Tigris, which was delivered to TWA in 1957 with registration N7316C, a designation it has kept since then.
More than 90% of the components and materials are being replaced in a process that has been running for nearly a decade.
The aircraft will look the same on the outside but pretty much every element inside has been removed and replaced at some point. And although the cabin will aim to recreate the look of the 1950s, modern ergonomic elements have been added to make sure passengers travel in comfort.
The aircraft has also been fitted with modern avionics and a state-of-the-art cockpit, turning an analog aircraft into a fully digital one. The Super Star has also been provided with all the necessary elements to guarantee modern standards of safety.
The need to get the necessary approvals for all these modifications has also added to the length of the project, which is being managed by a dedicated Lufthansa subsidiary, Lufthansa Super Star gGmbH.
The primary structure was completed in 2016 but its finish date and eventual use are not clear.
"Unlike the Ju-52, the Super Star is a long-haul aircraft. It would make little sense to have it operating only on short flights like the Junkers," says Weber.
Is this a hint that it may be used for long-haul luxury flying experiences? A sort of Orient Express of the air? "Maybe, nothing is decided yet," he replies.
The Landshut comes home
As if these two aircraft did not keep Lufthansa's technicians busy enough, another historical aircraft connected to the German airline has made headlines this year.
The Boeing 737-200 Landshut (D-ABCE) became the center of global attention 40 years ago when it was hijacked shortly after leaving Majorca by a Palestinian group requesting the release of imprisoned German Red Army Faction leaders.
After a six-day ordeal that included stops at six different airports in Europe and the Middle East as well as the murder of its captain, the Landshut was stormed by German special forces in Mogadishu, Somalia. All 86 hostages were liberated, while three kidnappers were killed and a fourth was wounded during the operation.
The Landshut was sold by Lufthansa in 1985. After serving a number of different airlines, it was retired to Fortaleza airport in Brazil in 2008.
In 2017 the German government bought it, and a complex logistic operation was set in motion to transport it back to Germany.
Lufthansa Technik specialists flew to Brazil to disassemble the aircraft and fit the different parts in a giant Antonov cargo airplane and an accompanying Ilyushin Il-76.
Once back home, it was reassembled at the Dornier museum in Friedrichshafen, where it is going to be fully restored and displayed in its original 1977 Lufthansa livery.
Although the Landshut is not expected to fly again, it is another relic of German commercial aviation history brought back to life.