The Government says no decision has been made about it when it might sell shares in Air New Zealand.
Business analyst Brian Gaynor said on Thursday there is a strong chance that the Government will sell off part of its stake in the the next couple of weeks.
The Government owns 73.4% of the national carrier and intends to sell down to 51% as part of its asset sale programme, but has not indicated when.
Associate Minister of Finance Jonathan Coleman said on Thursday that Finance Bill English has not made any final decision.
Mr Gaynor, the executive director of Milford Asset Management, said regulations about insider trading dictate when and how the Government sells the shares and the window of opportunity is small.
"The Government gets monthly accounts from Air New Zealand, therefore, it's considered to be an insider. Under the insider trading guidelines, the Crown cannot sell the shares after the first of December until the beginning of March. If it wants to sell them over the next two or three months it has to sell those shares by the end of November."
Mr Gaynor told Radio New Zealand's Morning Report programme on Thursday airlines are always considered a risky investment, but Air New Zealand has been doing well.
The Treasury denies there is only a small window of opportunity for the Government to sell the shares. A spokesperson said the Crown can trade regardless of such restrictions.
The spokesperson said ministers and Treasury officials who are involved in decisions about the Crown selling its shares in listed companies do not have any non-public information that would legally prevent the Crown from making the transaction.
The Government said it is still aiming for 85% of the asset to be owned by New Zealanders.
But Labour's state owned assets spokesperson Clayton Cosgrove said that is going to be difficult, as the company is already listed on the Stock Exchange and there is no initial public offering like Meridian Energy and Mighty River Power.
"It will be done through brokerage houses and the deal will be done with institutions. So that's not mum and dad being first in the queue, is it? And secondly, that's an early Christmas present for those foreign institutions and foreign brokerage houses."
