Claude Williams said Wednesday that he expected to make that announcement before the end of the week.
But Williams said Thursday that some details still need to be worked out.
The government committed in its 2013-14 budget to sell the King Air B200 as a cost-cutting measure.
The plane was used by the premier and members of cabinet.
Flying Colours Corp. of Peterborough, Ont., was hired in December as the broker to sell the plane.
Williams has said the plane is worth about $3.8 million, but Gary Wood, director of sales and marketing for Flying Colours, said in December he expected it would fetch between $2 million and $3 million.