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Mammoth Freighters adds UK facility for 777 cargo conversions

STS Aviation Services will begin modification work in 2024

The interior of a Boeing 777 factory-built cargo jet. After a conversion process, the cabin of a passenger jet looks the same way. (Photo: Jim Allen/FreightWaves)

Mammoth Freighters on Monday announced a new collaboration with STS Aviation Services to augment production capacity for passenger-to-freighter (P2F) conversions of the Boeing 777.

All work will be accomplished at STS’ facility in Manchester, United Kingdom, starting in mid-2024. The multiyear agreement covers both the 777-200LR and 777-300ER aircraft.

Mammoth Freighters, an aerospace newcomer fueled by resources from Fortress Investment Group, is one of two companies pioneering the conversion of used 777 aircraft into all-cargo jets after being discharged from passenger flying. Boeing sells factory-built 777 freighters, but until now there hasn’t been a conversion program for the large widebody jets.

Orlando, Florida-based Mammoth’s primary conversion facility is at Fort Worth Alliance Airport in Texas. The former American Airlines maintenance facility has 840,000 square feet of space, six widebody hangar bays and overhead cranes for modification and maintenance work. 


The aerospace company last week announced AviaAM Leasing as one of its first customers and says it has 29 firm orders to date. 

“Ensuring that we have the right modification capacity in place around the world to meet the robust demand for the Mammoth 777 freighter program is vital to our success,” said David Steinmetz, Mammoth’s senior vice president of operations, in a news release. “STS has the experience, knowledge, capability and, most importantly, the high-quality reputation that we look for in an MRO [maintenance, repair and overhaul] partner.”

The STS facility will also provide Mammoth with urgent aircraft maintenance, product support and spares provisioning throughout Europe. STS, an aircraft maintenance and parts provider based in Melbourne, Florida, acquired the Manchester facility earlier this year as part of an expansion effort. It is the company’s third facility in the U.K.

“This P2F program assures stability in Manchester from day one and means we can forge ahead, investing in entry-level engineers and trainee schemes giving them development opportunities in the area of major programs and real-life aircraft engineering,” said STS Managing Director Ian Bartholomew.


Mammoth is developing its prototype freighter and plans to begin commercial production next year once it receives U.S. government certification of its 777 conversion design.

Meanwhile, Miami-based conversion specialist Aeronautical Engineers Inc. said Aviation Holdings III Investments placed an order for its twelfth Boeing B737-800 freighter conversion. Retrofit work is scheduled to begin in February. 

Also, Titan Aircraft Investments, the joint venture between Atlas Air Worldwide (NASDAQ: AAWW) subsidiary Titan Aviation Holdings Inc. and Bain Capital Credit, announced the placement of a Boeing 737-800 converted freighter on long-term dry lease with Dublin-based ASL Aviation Holdings.

Click here for more FreightWaves/American Shipper stories by Eric Kulisch.

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Eric Kulisch

Eric is the Supply Chain and Air Cargo Editor at FreightWaves. An award-winning business journalist with extensive experience covering the logistics sector, Eric spent nearly two years as the Washington, D.C., correspondent for Automotive News, where he focused on regulatory and policy issues surrounding autonomous vehicles, mobility, fuel economy and safety. He has won two regional Gold Medals and a Silver Medal from the American Society of Business Publication Editors for government and trade coverage, and news analysis. He was voted best for feature writing and commentary in the Trade/Newsletter category by the D.C. Chapter of the Society of Professional Journalists. He won Environmental Journalist of the Year from the Seahorse Freight Association in 2014 and was the group's 2013 Supply Chain Journalist of the Year. In December 2022, Eric was voted runner up for Air Cargo Journalist by the Seahorse Freight Association. As associate editor at American Shipper Magazine for more than a decade, he wrote about trade, freight transportation and supply chains. He has appeared on Marketplace, ABC News and National Public Radio to talk about logistics issues in the news. Eric is based in Vancouver, Washington. He can be reached for comments and tips at ekulisch@freightwaves.com