The international debut of the U.S. F-35 Lockheed Martin Joint Strike Fighter in the U.K. this month could obscure a formal agreement between London and Paris to begin work on its potential replacement.

In January, when France and the U.K. signaled plans to cooperate on a €200-million ($374 million) concept study for an unmanned future combat air system (FCAS), Europe’s two biggest defense spenders said a memorandum of understanding could follow at the Farnborough International Airshow in July, with a subsequent contract expected this fall.

“We hope to achieve that shortly,” Philip Dunne, Britain’s defense procurement chief, said during the Eurosatory exposition here June 19, emphasizing the significance of the F-35’s impending arrival.

In the meantime, Dunne told reporters the two nations are “working in parallel on protocols concerning data-sharing” to enable collaborative efforts in support of the two-year FCAS study, which is expected to build on new unmanned combat air system (UCAS) demonstrators developed in Britain and Europe in recent years.

The U.K. Defense Ministry’s £185 million ($300 million) Taranis, led by BAE Systems, conducted its first flight last August. Initiated in 2006, the Defense Ministry has kept the program under a veil of secrecy, including aspects of its exterior design, which BAE says remain classified. Similar in size to a BAE Hawk jet trainer, Taranis is powered by the same single Rolls-Royce Adour turbofan fitted to the French-led nEUROn UCAS demonstrator, though no firm decision has been made on the powerplant for the larger, Franco-British FCAS.

The six-nation nEUROn, meanwhile, completed its first flight demo in France in December 2012. Led by Dassault Aviation and the French arms procurement agency DGA, the €405-million stealthy UCAS demonstrator is midway through a two-year trial, with between 50 and 60 flight tests already complete.

“We have met all the goals set for our tests,” says an industry official familiar with the program, adding that flight testing is continuing in France before moving to Italy this year for additional radar cross section tests. The nEUROn trials will then move to Sweden in 2016, culminating in a weapons drop test at the Vidsel range in northern Sweden.

In May, Dassault demonstrated nEUROn’s ability to fly in formation with manned aircraft, including a
Rafale fighter and a Falcon 7X business jet. The flight marked the first time that a combat UAV has flown in formation with other aircraft, offering a glimpse of how the French and U.K. air forces could employ a mix of manned aircraft, civil assets and UCAS systems in the future.

Meanwhile, if a contract for the two-year FCAS concept study is awarded this year, the project will see BAE and Dassault evaluate key technologies in preparation for a joint demonstration of a future UCAS targeted for 2020.

“This will be a study of how to mix the French and British capabilities and meet force requirements,” including those related to low-observability and mission systems, the industry official says.

However, both companies expect to bring more than just technical experience to their future partnership on unmanned systems, assuming the Franco-British effort continues. Beyond BAE, Dassault, and their respective top-tier suppliers, the partnership still needs to establish workshare arrangements not yet settled, though preliminary work on that topic has taken place.

Ultimately, the proposal for a four-year demonstration phase—which is expected to top €1 billion—could rely on multiple vehicles to serve as technology testbeds. In addition to a demonstrator combining some aspects of Taranis and Neuron, these could include less-costly simulators and manned platforms, such as using a Dassault Falcon to test infrared sensors.

“The biggest driver is the budget,” the industry official said. “We may even reuse Taranis or nEUROn.”

Securing government backing to fund the follow-on demonstration phase could prove challenging, however. With the U.K. expected to publish a new strategic defense and security review within a few months of a new government taking office next year, and French presidential elections to follow in early 2017, a decision on funding a joint UCAS demonstrator is likely to be delayed to 2018 or beyond.