M won the brief from GA following a three-way pitch, which also involved Cubitt Consulting.
M consultants Louise Tingstrom, Jane Astrid More and Joanna Darlington are handling the account, which is thought to be more IR-focused than the corporate and financial brief GA previously held.
The account is believed to be worth around £150,000.
Although Air France chairman and CEO Jean-Cyril Spinetta planned to direct the final stages of the pitch, it is thought that these were handled by head of IR Dominique Barbarin.
Barbarin is a former corporate director at GA's Paris office.
GA's Paris office originally started working for Air France in 1998, when the firm picked up the lucrative brief to handle PR around the then state-owned company's partial-privatisation via a flotation of the company on the Parisian stock market TK (PRWeek, 12 June 1998).
The company is a member of France's CAC 40 index, which comprises the country's top 40 companies by market capitalisation.
The appointment of M to handle the pan-European IR brief follows a 33 per cent rise in Air France's pre-tax profits at a time when airlines on the Continent are struggling with high fuel prices and overcrowding in the sector.