Noel Forgeard, the former co-chief executive of EADS, has become the first to be placed under formal investigation for alleged insider dealing in a criminal inquiry that threatens to destablise the Franco-German aerospace group at a critical moment in its recovery.

Mr Forgeard spent 35 hours in the custody of the Paris financial brigade and was released after posting a €1m ($1.55m) bond late on Thursday night. Jean-Alain Michel, his lawyer, told the Financial Times that Mr Forgeard continued to maintain his innocence.