PARIS (Reuters) - The chief executive of French planemaker Dassault Aviation raised the prospect of an alternative plan on Friday if talks between France, Germany and Spain on a joint fighter plane break down, but said he still believes in the project. German Chancellor Angela Merkel and French President Emmanuel Macron first floated the venture in 2017 but it has become mired in mistrust and differing visions between Berlin and Paris as well as corporate infighting over workshare, people close to the talks have said. Spain’s decision to join the project last year further slowed discussions. “I don’t believe it’s in mortal danger but I’m not going to tell you that the patient is not in difficulty,” Dassault’s CEO Eric Trappier said of the project formally launched in 2019. “The head of a company must always have a Plan B in mind. He does everything to ensure Plan A succeeds, everything. But the day Plan A doesn’t work you need a Plan B,” he told a news conference when asked what would happen if the talks failed. Trappier said Dassault had accepted that European planemaker Airbus would have a larger overall share under an equal three-way split agreed by the partners, since it represents the military aircraft industries of both Germany and Spain. But that did not mean all parts of the work could be split equally with no clear leadership, he added. A key stumbling block concerns the control of technologies like flight controls, for which France claims the upper hand since Dassault builds fighter planes and business jets on its own and Airbus has its civil engineering offices in Toulouse. “If nobody is running flight controls it’s not possible, it won’t work: you have to have someone in charge,” Trappier said. He played down a separate dispute over access to know-how, saying Dassault and Airbus had a shared industrial understanding of the way intellectual property is protected. That discussion is mainly being conducted at a political level, he added. Trappier said a merger between FCAS and the BAE Systems-led Tempest project involving Britain, Sweden and Italy was “not on the agenda”.