U.S. Army's Russian Mi-171E helicopter used for secret operations spotted flying in Arizona.

A Russian-built Mi-171E helicopter operated by the U.S. Army Aviation Technology Office (ATO) was observed returning from a local flight near Phoenix on January 31, 2026.

On January 31, 2026, the X account venom13 managed to take two pictures of a Russian-built Mi-171E helicopter returning from a local flight near Phoenix, Arizona. Possessing the serial number 14-0184, this particular Mi-171E can be associated with the Aviation Technology Office (ATO), a secretive unit of the U.S. Army that evaluates foreign aircraft and supports special operations where conventional U.S. military attribution is undesirable.
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The Mi-171E can carry up to 27 passengers on foldable seats in a standard transport configuration. For cargo missions, it is rated to transport up to 4,000 kilograms internally within the cabin or on an external sling. (Picture source: X/venom13)

This sighting attracted attention because this specific Mi-171E, with the serial number 14-0184, belongs to the Aviation Technology Office (ATO), a U.S. Army's secretive unit which operate in situations where visibility, attribution, and standard U.S. military signatures would be a problem, including missions connected to the Joint Special Operations Command. Aircraft linked to the unit include Mil Mi-17 and Mi-171 helicopters, Bell 407 and Bell 429 light helicopters, MD Helicopters MD-500 series aircraft, and Beechcraft King Air turboprops. This diversity allows ATO crews to operate and evaluate aircraft commonly encountered in foreign military and paramilitary forces, but also allows missions to be conducted with plausible deniability, meaning that the presence of U.S. forces or U.S. support is not immediately apparent or formally attributable.

The history of the Aviation Technology Office (ATO) begins on March 2, 1981, with the establishment of a covert U.S. Army aviation element commonly referred to as SEASPRAY. This unit was created to provide aviation support that could not be attributed to conventional U.S. military forces and initially operated under the cover designation “1st Rotary Wing Test Activity.” Its early fleet included unmarked Hughes 500D helicopters and later expanded to fixed-wing aircraft such as Cessnas and Beechcraft King Airs, often registered through civilian-linked structures rather than standard U.S. Army channels. During the 1980s, SEASPRAY operated from locations including Tampa, Florida, and supported missions primarily connected to Central America. By the late 1980s, the unit was absorbed into Delta Force as its dedicated aviation component, known as E Squadron, before reemerging in the 1990s under the Flight Concepts Division name and later adopting the Aviation Technology Office designation by the 2010s, while remaining administratively linked to the Army Aviation Flight Test Directorate at Fort Eustis, Virginia.

The mission set of the ATO, one of the most secretive U.S. Army unit, combines direct operational aviation support with systematic evaluation of non-standard U.S. aircraft and systems. Operationally, the ATO is said to conducts discreet insertion and extraction of personnel, transport of sensitive cargo, and aviation support for missions where overt military aviation would be politically or operationally unsuitable. These operations typically involve small numbers of aircraft, limited personnel, and short-duration deployments, with aircraft configured to blend into civilian or host-nation aviation environments through neutral markings or foreign designs. In parallel, ATO evaluates aircraft types, avionics, communications, and navigation systems that are not part of standard Army inventories, including foreign-built helicopters such as the Mi-171. This evaluation includes performance in hot and high conditions, austere landing zones, and long-range navigation profiles, with findings directly informing operational readiness rather than serving purely developmental or research purposes.

Across its earlier and current forms, ATO is associated with providing aviation support to elite U.S. units operating under national-level tasking rather than conventional forces. During the SEASPRAY and E Squadron periods, the unit is linked to direct aviation support for Delta Force missions requiring civilian-style or deniable flight profiles. In later phases as the Flight Concepts Division and Aviation Technology Office, it is associated with broader Joint Special Operations Command tasking, supporting multiple JSOC elements that require discreet aviation access. While specific operations are not publicly detailed, repeated associations with Delta Force, JSOC-directed missions, and intelligence-supported activities indicate a consistent role as an aviation enabler for small-unit operations where attribution, basing, and visibility must be minimized, or even possibly be denied, explaining the presence of Russian helicopters, such as the Mi-171E 14-0184, in the U.S. Army.

The Russian Mi-171E is an export-designated variant of the Mi-8AMT within the Mi-8/Mi-17 helicopter family developed by the Mil design bureau. The helicopter first flew in 1991 and entered operational service in 1992, with serial production centered at the Ulan-Ude Aviation Plant, while related Mi-8 and Mi-17 variants have also been manufactured at the Kazan Helicopter Plant. The Mi-171E retains the basic Mi-8 airframe layout, including a conventional fuselage with a rear cargo compartment and side doors, while incorporating updated propulsion and systems compared with earlier Mi-8MT configurations. It was developed to meet export requirements for government and state operators rather than purely commercial aviation users.

The Mi-17 is a twin-engine medium transport helicopter powered by two Klimov TV3-117MT turboshaft engines, with later configurations integrating VK-2500 engines. Engine output in VK-2500 variants reaches 2,400 hp in takeoff mode and up to 2,700 hp for limited-duration emergency power, improving performance in high-temperature and high-altitude environments. The helicopter is equipped with a five-bladed main rotor and a tail rotor, with upgraded versions incorporating composite rotor blades and, in some cases, an X-shaped tail rotor to improve controllability and reduce acoustic signature. An auxiliary power unit is fitted, enabling autonomous engine starts and onboard power generation, including starts at elevations up to 6,000 meters.

In terms of payload and capacity, the Mi-171E can carry up to 27 passengers on foldable seats in a standard transport configuration. For cargo missions, it is rated to transport up to 4,000 kilograms internally within the cabin or on an external sling, with later upgrade packages increasing the external sling load limit to 5,000 kilograms. The helicopter can be configured for multiple roles, including troop transport, cargo resupply, medical evacuation with stretcher installations, and government utility missions. Its fixed landing gear and structural design allow operations from unprepared or semi-prepared landing sites, including remote and austere locations with limited ground infrastructure.

Operationally, the Mi-171E has been supplied primarily to military, paramilitary, and government operators across Asia, Africa, Latin America, and Eastern Europe. The type has been used for logistics support, personnel transport, disaster response, search and rescue, and internal security tasks, reflecting its multi-role configuration rather than specialization for a single mission set. By 2014, the wider Mi-8 and Mi-17 family had exceeded 12,000 units produced worldwide, had been delivered to more than 100 countries, and had accumulated a combined fleet flight time of over 100 million hours, with at least 265 Mi-171 produced. This widespread distribution explains why the Mi-171E remains relevant for state users and specialized units that require familiarity with one of the most commonly operated medium transport helicopters globally.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.