Richard Santulli, the chairman and chief executive of Berkshire Hathaway Inc NetJets Inc and long considered a possible successor to Warren Buffett, has stepped down, effective immediately.

Santulli, who is in his mid-60s, said in a statement he is leaving to spend more time with his family and to pursue other interests. He said he will remain with NetJets as a consultant for at least a year. Santulli said he informed Buffett of his decision on Tuesday morning.

Buffett appointed David Sokol, the chairman of Berkshire's MidAmerican Energy Holdings Inc and also considered a top candidate to eventually run Berkshire, as NetJets' chairman and interim chief executive.

NetJets specializes in fractional aircraft ownership, which lets individuals and companies buy shares of private jets rather than full ownership. Buffett uses NetJets aircraft for his own business travel.

It is with reluctance that I accept Richard's decision to step down, Buffett said in a statement. Richard Santulli is synonymous with the fractional jet ownership industry and his vision and energy has made NetJets the leader that it is today. All of Richard's friends at Berkshire Hathaway wish Richard well in this transition.

Buffett, Santulli, Sokol and their respective companies were not immediately available for further comment.

Berkshire Class A shares closed Tuesday up $310 at $100,310 on the New York Stock Exchange. (Reporting by Jonathan Stempel; editing by Andre Grenon)