According to an interview conducted by Thomas P. Ehrhard,
Aquiline was a stealthy propeller-driven, low altitude, anhedral-tailed UAV called Aquiline and designed for low-level electronic
surveillance of the Chinese nuclear program. Aquiline was designed by McDonnell Douglas in the late 1960s and advanced to flight testing, but never saw operational use due to reliability problems. The aircraft was to be controlled by data link from a high-flying U-2.
Air Force UAVs: The Secret History
The UAV section is in Appendix E.
Here's the motivation for Aquiline's development,
In the early 1960s. there were many problems in obtaining coverage of hostile territory. The U-2 was too vulnerable ro Soviet sur- face-to-air missiles, as had been demonstrated by losses over the Soviet Union, Cuba. and the People's Republic of China. The OXCART was still under development and even when completed might prove vulnerable to Soviet radars and missiles. Although safe from interception, the newly developed photosatellites could not pro- vide coverage of a desired target on short notice. Because several of the intelligence community's primary targets such as Cuba and the new Soviet radar installation ar Tallinn (Estonia) were not located deep in hostile territory, CIA scientists and engineers began to con- sider the possibility of using small, unmanned aircraft for aerial reconnaissance. They believed that recent advances in the minia- turization of electronic technology would make possible the development of a reconnaissance vehicle with a very-low-radar cross section and small visual and acoustical signatures. Such a vehicle could reconnoiter an area of interest without the hostile country real- izing that it had been overflown.
[Aquiline] was essentially a powered glider with an 8.5-foot wingspan. The aircraft weighed only 105 pounds. Aquiline's tail-mounted engine drove a two-bladed propeller. Powered by a small 3.5-horse-power two-cycle engine originally developed by the McCullough Corporation for chainsaws.
Here's a bit from the appendix on Axillary,
While Project AQUILINE was still under development, its chief aero- dynamicist, Charles N. Adkins, left the program because he believed that its escalating costs would prevent it from ever producing a de- ployable aircraft. He wanted to build a small. inexpensive remote-controlled aircraft to test a low-cost lightweight autopilot currently being developed by ORO. Under a $5,000 time-and-materials contract with Melpar Incorporated. Adkins hired a local model aircraft builder to assemble and modify a standard Hawk-750 glider kit and power it with a rear-mounted engine and pusher propeller. Following a series of successful test flights, Adkins installed a small camera and took a number of aerial phorographs . By this time the effort to build a "Miniature Multi-Purpose Airborne Vehicle" had become known as Project AXILLARY. Melpar, Inc. received a second contract for $50,000 to install ORO's autopilot in the aircraft, and the project managers now began searching for a use for their vehicle . The two main possibilites were (1) as a short-range reconnaissance vehicle for use in a peace-monitoring or intelligence-gathering system and (2) as a short-range warhead delivery system. In 1971 the Office of Special Activities evaluated AXILLARY flight-testing and determined that the small model air-craft was not suitable for use as a covert reconnaissance vehicle because of its large radar cross section and significant accoustical signature. The aircraft's radar signature made it potentially useful as a weapons system, however. ORD suggested that AXILLARY be equipped with a radar-homing unit [REDACTED] which would make it an inexpensive means for [REDACTED] surface-to-air missile systems in North Vietnam.