For more than 20 years, as Qantas Club members walked up the stairs to the inner sanctum in the Sydney airport, they could see Brett Whiteley’s 2×2.4-metre flamboyant painting of the Opera House looming above them.

One of the directors of the Flying Kangaroo saw the work in 1982 and bought it for probably less than $200,000 — a high price for any painting at the time, although Whiteley had the status of a pop star and his pictures have always been expensive. Now the painting is the centerpiece of Sotheby’s next auction in Sydney on 7 May when that $200,000 picture is expected to break the current Australian auction record of $3.2 million and even reach $4 million.

As art consultant Jon Dwyer says, the corporate raiders in Texas who are trying to buy Qantas must be wondering how the company comes to be flogging off some of its assets. But Sotheby’s former managing director, Mark Fraser, says the deal had been struck and a contract signed long before the buyout had been proposed.

Dwyer has been an art director with Leonard Joel and Christie’s for more than 20 years and once tried to talk Qantas chief Geoff Dixon into allowing Christie’s to sell the collection. Still, as he admits, the 22 pictures could only be ranked as a “boutique corporate collection”. Apart from the Whiteley and a Charles Blackman — Dream in a Cat’s Garden that graced the Qantas Club lounge in Melbourne for years (and which could fetch $350,000 or more) — most of the rest of the works are not top-shelf and most are likely to fetch $20,000 or less.

But if the Whiteley does break the current record — set by John Brack’s The Bar at a Sotheby’s auction last year — then the collection could generate more than $5 million — about as much as Qantas earns from flying a full complement of passengers from Melbourne to Cairns. Sotheby’s is also suggesting the sale of 115 works could exceed $13 million which would make it the biggest, mixed-vendor art sale ever held in Australia.

Jon Dwyer says the current record was set in 1988 when Leonard Joel put 1200 lots under the hammer over three days and generated almost $10.5 million. Alan Bond helped by paying $1.25 million — a top price at the time — for a Rupert Bunny that was lost in a mysterious fire in London years later.

Under Fraser’s directorship, Sotheby’s switched from holding sales of hundreds of mediocre pictures with a few high-quality works to restricting numbers to less than 200 and aiming to have as many high-priced paintings as possible. The latest auction includes a John Peter Russell of one of his Belle-Ile pictures that carries an upper estimate of $1.2 million and a Eugene von Guerard of cabbage trees near the Shoalhaven River from the colonial artist’s only trip to New South Wales which could fetch $400,000.

With the art market awash with cash, these are challenging times for collectors.