NASA is moving ahead with plans to evaluate whether a Boeing 737-73W aircraft—currently tied to a classified U.S. Air Force program—can be converted into a next-generation reduced-gravity test platform, in a development that blends routine aerospace procurement with an unusual layer of military secrecy.
The effort, disclosed through a recent contracting notice from NASA’s Armstrong Flight Research Center, centers on a sole-source award to Denmar Technical Services, Inc., a Nevada-based aerospace contractor already embedded in sensitive Air Force modification work. The goal is to determine whether the aircraft can be adapted into a parabolic-flight “reduced gravity” testbed, commonly known in aerospace circles as a “Vomit Comet” due to the intense maneuvers used to simulate weightlessness.
But the aircraft in question is not a standard research jet. It is currently owned by the U.S. Air Force and is described in procurement documents as part of a classified program, raising immediate speculation that NASA may be indirectly stepping into a much deeper military aviation ecosystem than is typical for its test aircraft fleet.
According to NASA’s notice, Denmar Technical Services will be responsible for conducting a feasibility assessment of the Boeing 737-73W’s suitability for reduced-gravity missions. The contractor would also be required to modify the aircraft’s cabin, perform overdue maintenance and airworthiness restoration, and repaint the exterior with NASA identifiers if the aircraft is approved for use.
The scope is unusually broad for a feasibility study, effectively placing Denmar in charge of evaluating, repairing, and potentially converting the aircraft in parallel with its ongoing classified Air Force obligations.
NASA stated that the aircraft, if cleared for service, would support the agency’s Reduced Gravity Test Bed Project, enabling validation testing of space suits and crew systems for the upcoming Artemis program. The agency’s contracting language explicitly notes the urgency: modifications must be completed no later than October 1, 2026, to support near-term space suit testing schedules.
The notice further explains that the aircraft will be transferred from the Air Force to NASA after completion of closeout tasks, underscoring the unusual nature of a handover involving a still-classified platform.
Reduced-gravity aircraft are not new to NASA. For decades, the agency has used parabolic flight profiles—sharp climbs followed by controlled dives—to create brief periods of weightlessness. These flights are essential for astronaut training, microgravity research, and hardware validation before spaceflight.
The most well-known provider of such services today is Zero Gravity Corporation, which operates modified aircraft such as a Boeing 727-200 known as “G-Force One.” These flights are characterized by steep pitch changes that produce alternating periods of hypergravity and near-weightlessness inside the cabin.
NASA’s renewed interest in expanding or modernizing its reduced-gravity fleet reflects growing demands from the Artemis program, the agency’s initiative to return humans to the Moon. The program recently reached a milestone with Artemis II, a crewed lunar flyby mission that demonstrated deep-space human operations without landing on the lunar surface.
Future missions, including a planned crewed lunar landing targeted for 2028, will require extensive validation of next-generation space suits and mobility systems designed for the Moon’s one-sixth gravity environment. That testing cannot be fully replicated in simulation alone, making parabolic aircraft flights a critical bridge between laboratory development and lunar deployment.
While NASA’s notice does not explicitly identify the aircraft by tail number, aviation analysts have focused attention on a Boeing 737-73W registered as N712JM, which has long been linked to U.S. government flight test activity and unusual modification work.
FAA records indicate the aircraft was originally delivered in 2013 to East West Bank through a leasing structure involving Wells Fargo Bank before being acquired by Denmar Technical Services in 2019. In 2020, ownership or operational control shifted into the U.S. Air Force system.
At that time, the aircraft drew attention for its unusual external appearance, including a green protective primer coating typically seen on newly manufactured or heavily modified airframes. Observers noted visible instrumentation and wiring routed into the cabin area—features more consistent with experimental flight testing than commercial service.
The aircraft was later observed conducting test flights out of Santa Maria Airport in California under the callsign “STING 38,” with operations over restricted U.S. military ranges off the Southern California coast. Its flight behavior included non-standard profiles that suggested specialized instrumentation or aerodynamic testing.
Despite this activity, the aircraft’s purpose has never been officially disclosed.
What makes the NASA proposal particularly sensitive is the aircraft’s current ownership. According to NASA’s own documentation, the Boeing 737-73W is owned by the U.S. Air Force and is embedded in a classified program. Denmar Technical Services is already contracted by the Air Force to perform modification work on the aircraft, giving the company unique access that NASA acknowledges it does not possess.
The contracting notice explicitly states that NASA does not have a “need to know” regarding existing modifications performed under the Air Force program. As a result, Denmar is effectively serving as a technical intermediary between two federal agencies with vastly different access requirements.
The Air Force will retain control of the aircraft until its classified work is complete, after which ownership will transfer to NASA.
This arrangement is highly unusual in civilian aerospace procurement, where aircraft conversions are typically conducted on platforms already under NASA or contractor control.
The announcement has inevitably revived comparisons with another highly classified Boeing 737 variant: the NT-43A, widely known by its callsign RAT55. This aircraft is a heavily modified Boeing 737-200 series used for airborne signature measurement and tracking, and is often described as one of the most secretive aircraft in the U.S. inventory.
The NT-43A has been associated with long-term operations out of Tonopah Test Range Airport in Nevada and has recently been observed supporting various test and evaluation activities linked to modern defense and space programs.
However, NASA’s contracting notice makes clear that the aircraft under consideration is not the NT-43A, but instead a much newer 737-700-series airframe. That distinction is significant: while the NT-43A is a Cold War-era platform adapted for specialized measurement tasks, the 737-73W under discussion appears to be a modern airframe embedded in a separate, more recent classified program.
Denmar Technical Services, Inc., based in Reno, Nevada, has emerged as a key player in specialized aerospace modification work. The company describes its capabilities as including mission system development, sensor integration, and advanced airborne testing systems.
Its portfolio also includes work in infrared and radiofrequency survivability, as well as software-driven mission analysis tools. These capabilities align closely with defense-oriented aerospace programs that require integration of sensors, emissions control, and real-time data processing.
The company is widely believed to have played a central role in modifying classified Air Force platforms, including the NT-43A program, though official confirmation remains limited due to program sensitivity.
NASA’s decision to award a sole-source contract to Denmar reflects the agency’s assessment that no other contractor has the necessary access or technical knowledge to work on the aircraft without disrupting its classified configuration.
The identity and purpose of N712JM remain uncertain, but aviation tracking data and sightings over the past several years have fueled speculation that it may be part of a broader fleet of modified 737s operated by the U.S. Air Force for research, development, and operational testing.
Some analysts have suggested possible links to Air Force serial designations such as 21-0024, though this connection remains unconfirmed. Other reports have placed similar aircraft at facilities operated by Sierra Nevada Corporation, a major defense contractor known for spacecraft and specialized aviation systems integration.
Recent flight tracking data have even suggested intermittent activity near Colorado Springs Airport, adjacent to Peterson Space Force Base, though no confirmed flight operations have been publicly recorded in recent months.
The lack of transparency surrounding these aircraft reflects a broader pattern in modern defense aviation programs, where modified commercial platforms are increasingly used for intelligence, testing, and advanced systems integration.
What distinguishes the current proposal is not just the aircraft itself, but the urgency behind NASA’s timeline. The agency’s Artemis program places significant pressure on hardware validation schedules, particularly for space suits and human mobility systems designed for lunar operations.
NASA’s notice emphasizes that reduced-gravity testing must proceed quickly to support upcoming mission milestones. With a target lunar landing date set for 2028, the agency is working to accelerate pre-flight validation cycles.
If the Boeing 737-73W is successfully converted, it could become a central asset in bridging Earth-based testing and lunar operational readiness.
The proposed aircraft conversion highlights an unusual intersection between civilian space exploration and classified military aviation programs. A NASA-owned reduced-gravity aircraft built from a currently classified Air Force platform would represent one of the most tightly coupled civil-defense aerospace collaborations in recent years.
For now, much remains unknown: the aircraft’s exact identity, its current configuration, and the scope of its classified modifications all remain undisclosed.
What is clear is that NASA is willing to leverage highly sensitive military aviation assets to support its next phase of human space exploration—and that the line between experimental aerospace research and classified defense programs continues to blur in unexpected ways.
As Denmar Technical Services begins its feasibility assessment, the aerospace community is likely to watch closely for any signs of what this mysterious Boeing 737-73W truly is—and what role it has already been playing behind the veil of classification.
