The Gupta family have argued, in their application to appeal a high court ruling to ground their plane, that the court made a number of errors, including believing that the Canadian export bank which facilitated the lease deal would suffer reputational harm.
The papers also state that the South Gauteng High Court in Johannesburg erred on a number of issues during the judgment, in which the Guptas were ordered to return the plane to Lanseria Airport pending a court case in the UK.
Export Development Canada (EDC) and Stoneriver approached the court in March with an urgent application to have the aircraft grounded.
The Guptas had a lease agreement with EDC and Stoneriver for the Bombadier Global 6000 aircraft but are currently engaged in a legal dispute in UK courts over the agreement.
The applicants asked the court in South Africa to ground the plane until a final order was made, and to prevent its movement while the tracking system was switched off.
Judge Fayeeza Kathree-Setiloane found there was "a clear risk" of the aircraft being seized by the National Prosecuting Authority's Asset Forfeiture Unit to recover money from the Guptas.
The judgment further read: "This begs the question: Why would the Gupta respondents not want anyone to track the whereabouts of the aircraft? This makes for the pungent possibility that this was done so that the aircraft can be used for unlawful purposes," she said.
"Although the Gupta respondents dismiss this as 'baseless speculation that [does] not warrant a response', they conspicuously do not say that the aircraft is not being used for unlawful purposes and they do not give an undertaking that the aircraft will not be used for unlawful purposes in the future."
But in their application for leave to appeal, the Guptas argued that there were "compelling reasons why an appeal should be heard", and that they believed they had "reasonable prospects of success".
"The court erred in having assumed that the aircraft would deteriorate if the [Guptas] continued to use it... and was not entitled to come to this conclusion," the family said.
Further, the Guptas argued that the court made a mistake in believing that ECD and Stoneriver would run the risk of "reputational harm of being associated with 'the Gupta respondents' through their continued use of the aircraft".
"On [ECD and Stoneriver's] own version, they entered into the aforesaid agreements at a time when they must have known of the alleged controversy behind the Gupta family, as the allegations of alleged unlawful activity on their part had enjoyed widespread and frequent coverage in the... media," the Guptas argued.
Further, the Guptas state that the court was misdirected in finding that a failure to provide audited financial statements from the Guptas constituted an event of default.
They also contend that: "The court erred in holding the delisting of Oakbay Resources was material. The court ignored the fact that it voluntarily delisted itself from the Johannesburg Stock Exchange."