The Stratospheric Observatory For Infrared Astronomy, abbreviated as SOFIA, was an 80%/20% joint project between the United States’ NASA and Germany’s DLR. NASA was responsible for operating and maintaing the aircraft, while DLR was mostly responsible for science and telescope-related operations. The modified 747 replaced the Kuiper Airborne Observatory, a modified C-141 Starlifter with a significantly smaller telescope. The project was terminated on the 29th of September 2022, after 921 missions.
The aircraft, Serial Number 21441 and Line Number 306, was originally built as a 747SP for Pan American World Airways, being registered as N536PA. It was named “Clipper Lindbergh”, honoring Charles Lindbergh, an American Aviator who made the first non-stop flight between New York and Paris. The aircraft was delivered on the 6th of May 1977, however, on the 20th of May, Pan Am invited Anne Lindbergh, Charles’ widow, to christen the aircraft on the 50th anniversary of her husband’s historic flight.
In the 1980s, following the airline deregulation act, Pan Am entered a crisis it would never recover from, closing its wings in December 1991. In a desperate attempt to save itself, the airline sold its transpacific assets to United Airlines, including its entire fleet of 747SPs. N536PA was re-registered as N145UA, and repainted into United Airlines’ “rainbow” livery. The aircraft also had its name removed.
Between 1993 and 1994, the aircraft was repainted into United’s new identity, known as “Battleship Grey” - it would be the only 747SP painted in these colours. As new Boeing 747-400s were delivered, as well as upcoming Boeing 777 deliveries, which United Airlines would be the launch costumer for, the old 747SP fleet was retired during the first half of the 1990s. N145UA would be retired in October 1994, and stored at Las Vegas.
A flying telescope has two primary advantages: it can be used at high altitudes, avoiding most of the interference caused by Earth’s atmosphere, and it can be used anywhere in the world. In 1995, Kuiper Airborne Observatory was retired, and a replacement was needed. In April 1997, the Universities Space Research Association purchased N145UA from United Airlines for use as an airborne observatory. The 747SP was an aircraft with excellent capabilities as a flying telescope, having the highest service ceiling of any subsonic airliner, tied with the 747-400, an exceptional range, as well as a huge internal volume, allowing the installation of a much bigger telescope than the C-141 could fit. NASA acquired the aircraft from URSA in October of the same year, and conducted test flights before any major modification work commenced. Parts of another ex-United 747SP, N141UA, were purchased by Raytheon, to be used as a full-scale mock-up, ensuring the success of the modifications on N145UA.
Modification work began in 1998. Raytheon installed a 5.5m (18ft) tall (arc length) by 4.1m (13.5ft) wide door in the aft left side of the aircraft. This massive door could be opened in-flight, granting the telescope access to the sky. Additional modifications to the rear fuselage made sure there were no significant aerodynamic changes in the aircraft’s behaviour while the door was open. Most of the telescope was placed aft of a new pressure bulkhead, however the telescope’s focal point was located in the pressurized section of the fuselage, at a scientific instruments suite. This means that part of the telescope had to pass through the pressure bulkhead.
The telescope had a 2.5m (98in) diameter primary mirror - much larger than the 91.5cm (36in) primary mirror of Kuiper Airborne Observatory - and polishing was finished in December 1999, acheiving an accuracy of 8.5 nanometers. The hyperbolic secondary mirror, made of silicon carbide, was completed in May 2000. Since much of the telescope was manufactured in Europe, an Airbus Beluga was used to ferry these components to the United States, where they would be assembled into the 747.
On the 26th of April 2007, almost exactly 4 years before Infinite Flight would first be released, at the time exclusively for Windows Phone, the modified 747 performed its maiden flight. The first set of test flights were conducted with the door closed, to gather data on how the aircraft behaved with a massive telescope so far aft.
On the 21st of May 2007, Erik Lindbergh, Charles’ grandson, was invited by NASA to re-christen the aircraft with its former name, Clipper Lindbergh. On the 18th of December 2009, the massive door was opened in-flight for the first time, for a total of 2 minutes. On the 26th of May 2010, SOFIA saw first light (the first use of a telescope for a practical observation), returning images of the M82 galaxy’s core, as well as heat from Jupiter’s formation escaping through its cloud cover. Initial operation began in December 2010, and full operation started in 2014, with about 100 flights per year.
In December 2012, the aircraft received an upgraded glass-cockpit. The updated cockpit was based on the 747-400’s cockpit, however several elements have been modified, given SOFIA’s unique role. Unlike the MD-10, the modified SOFIA retained the flight engineer position. In Infinite Flight, the aircraft had a fully analog cockpit, identical to that of the 747-200.
The primary science objectives of SOFIA were to study the composition of planetary atmospheres and surfaces; to investigate the structure, evolution and composition of comets; to determine the physics and chemistry of the interstellar medium; and to explore the formation of stars and other stellar objects.
On the 29th of June 2015, Pluto eclipsed a distant star, with the resulting shadow being visible from New Zealand. SOFIA was sent to the region to study Pluto’s atmosphere. In early 2016, SOFIA detected atomic oxygen in Mars’ atmosphere for the first time in over 40 years, and, in early 2017, SOFIA helped to determine dwarf planet Ceres was covered in dust from other asteroids. In July of the same year, SOFIA conclusively observed a star occultation caused by a distant Kuiper Belt asteroid - which ground observations failed. This prompted the preparation of the New Horizons probe to visit said asteroid.
In October 2020, several spacecraft, as well as SOFIA, reported the presence of molecular water on the sunlit surface of the moon, and between January and May 2022, SOFIA was used to detect water on asteroids for the first time. The paper was published in February 2024.
As time went on, SOFIA kept getting older and harder to maintain. At around the same time, the infrared space telescope James Webb was also launched and started its observations. This prompted the astrophysics decadal survey for the 2020s to recommend recommended that NASA end SOFIA operations by 2023. “The survey committee has significant concerns about SOFIA, given its high cost and modest scientific productivity”.
The aircraft performed its last mission in September 2022, and, on the 13th of December 2022, was ferried to the Pima Air & Space Museum, in Tucson, Arizona, where it is now on display.
While there generally isn’t a lot to talk about an aircraft’s history in Infinite Flight, SOFIA’s Infinite Flight history may be just as unique as its real-life history, especially in the early days.
In mid-2011, Infinite Flight’s Windows Phone version 1.8 was released, featuring a Boeing 747-400 in House colours. The 747 would only be added for Apple devices in March 2012, on Infinite Flight’s iOS version 1.1.
Aircraft development at this time was extremely fast when compared to today’s standards, so this original 747 quickly became outdated. In November 2014, a new Infinite Flight update was released - and it was a big one. Not only the 747-400 was completely reworked, featuring a wide selection of liveries, but also a giant lineup of 747s were added, many with lots of liveries to choose.
Among the 747s added in this update, was, of course, SOFIA, and it was pretty special. Infinite Flight’s SOFIA featured a moving telescope door, with a modelled telescope inside. The door opened automatically upon reaching FL400, and closed automatically upon descending below that altitude. SOFIA also featured the unique single-slot flaps of the 747SP, meaning special care has been taken by not simply reusing the triple-slot flaps of all of the other 747 variants. If that wasn’t special enough, the way of acquiring SOFIA was radically different from other aircraft. The 747-400 remained free, however you had to pay for all other 747s - except SOFIA. Instead of buying SOFIA upright, the way to unlock it was to have at least 20 in-app purchases.
The aircraft has been mostly abandoned ever since. Following Global’s release, the telescope door was reworked so that it was a manual operation under the “Actions” tab. This has been a cause of intermittent issues, with the “Actions” tab disappearing from SOFIA on more than one occasion. When version 21.1 released, SOFIA mysteriously lost some of its main landing gear doors - an issue that has not been reported anywhere, as far as I know, and still present in-game. And, in January 2024, following the 24.1 update, SOFIA was removed from the free aircraft offering for those with previous in-app purchases. This was necessary, as the special SOFIA deal required custom coding that was slowing down future releases.
The ultimate nail in the coffin for SOFIA in Infinite Flight may be version 26.1. It was stated that the aircraft was removed from the game because it was too hard to carry over into the new content pipeline.
However, not all hope is lost. With version 26.1 featuring an Open Beta, I have figured out a small workaround to get SOFIA in the new version. I was shocked, and very pleasantly surprised to not only see that my workaround worked, but also that SOFIA, in fact, was carried over to the new content pipeline mostly unharmed - it has some shadow rendering issues, however, it is otherwise identical to the 25.1 version. I personally would much rather have a slightly buggy aircraft that is completely functional than to see it completely removed from the game. Hopefully, if this gains enough attention, SOFIA can be listed on the new aircraft list, and remain there until an eventual 747 rework - which will most likely see SOFIA and certain other 747 variants removed, given they’re already not easy to maintain, and there will be a significant quality difference between the reworked 747 variants and the outdated ones.
