Liverpool are not for sale, which is bad news for whoever paid for a plane to fly over Anfield ahead of Sunday's Premier League match against Manchester United carrying a protest banner that declared: "FSG Out -- Klopp In -- Enough Is Enough."

The timing of the stunt probably couldn't have been much worse. The subsequent 7-0 dismantling of United, Liverpool's biggest rivals, made the plane protest seem like the wrong idea at the wrong time.

Earlier this week, John W. Henry, Liverpool's principal owner, told the Liverpool Echo that his Fenway Sports Group's (FSG) commitment was "stronger than ever," despite an ongoing search for outside investment in the club. But, for some fans, FSG is holding Liverpool back and the time has come for new owners. It raises the question as to who, or what, are now deemed to be the perfect owners of football clubs by their supporters.

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FSG has certainly made mistakes since taking charge at Anfield in October 2010 -- backing the European Super League project and attempting to raise ticket prices without consulting fans have been two of their biggest errors -- but it has also transformed and revived one of football's most historic clubs through smart management and by hiring the best people to play out their vision.

Liverpool were on the brink of bankruptcy and maybe even liquidation when FSG, under the guise of New England Sports Ventures, bought the club for £300 million from previous owners Tom Hicks and George Gillett. Back then, Liverpool had gone 20 years without a league title, and although the club won the Champions League in 2005 they had been left behind by Manchester United, Chelsea and an emerging Manchester City.

There were some early missteps after taking charge at Anfield, such as the £35m club-record signing of Andy Carroll in their first transfer window at the helm. But from the moment FSG appointed Jurgen Klopp as manager in October 2015, to work in tandem with sporting director Michael Edwards, the vision of running a major football club in a sustainable but successful manner has been borne out.