The Falcon 900 plane belonging to Ben Ali's son-in-law Mohamed Sakhr el-Materi was held at Genevas Cointrin airport following the popular uprising that toppled the strongman's 23-year rule.
The plane was returned on Thursday, Le Temps newspaper reported.
But the foreign ministry confirmed only that a decision had been taken to return the craft to Tunisia, without saying when.
"The plane was the object of freezing measures ordered by the Swiss authorities against a number of people belonging to the entourage of former president Ben Ali," a statement said.
The ministry said the aim of the measures was to allow the return of illegally gained assets to the Tunisian people through the courts.
Its sale could bring in between $8 million and $8.5 million, according to Le Temps.
Switzerland followed several other countries in freezing the assets of Ben Ali and his clan after the uprising which led to Ben Ali's toppling in January.