Ppp healthcare chief executive Peter Owen resigned suddenly on Monday amid speculation that he is to take over as head of British Airways.
The former head of Irish national airline Aer Lingus has been in the post at PPP for less than six months.
He has extensive experience in the airline industry, including British Airways where he started his career.
BA's half-yearly pre-tax profits had fallen by 40% from £385 million to £240m.
PPP's parent group Sun Life, owned by Axa, denied that a boardroom split led to his departure.
Phil Hickley, at Sun Life, said: "The reports are mistaken, Owen still had an active part to play in the company."
Owen was appointed to the board of Sun Life last May, after successfully overseeing PPP's acquisition from Guardian Royal Exchange for £3.5 billion.
But he subsequently handed over responsibility for running the healthcare group on a day-to-day basis to Mark Adams who was appointed PPP's managing director.
Mr Adams is understood to report directly to Mark Wood, Sun Life's group chief executive.
Meanwhile, Owen set about leading the integration of Guardian's PPP business with Sun Life and undertaking a worldwide review of the Axa brand name.
He said in a press statement he had massively enjoyed his work, but had decided it was time to move on to another challenge.
Mark Wood in turn praised Owen's personal commitment and contribution to achieving Sun Life's merger with Guardian. He added: "We quite understand his wish to move on and we wish him well."