Oprah surprises her audience with a trip to Australia – on a plane flown by John Travolta

It was the opening show of her 25th and final season, and there was a feeling in the air that Oprah Winfrey would not let it pass by quietly. "This is really my last chance to do something really big," she told her trembling audience. "So I started to think about where would I most want to go . . ." By now the crowd had reached something close to religious ecstasy. Finally, she let them have it: "We're going to Australia!" And then they really lost control.

People were screaming and crying. The front of an airliner burst through the back of the set, a cardboard Qantas check-in desk joined it, confetti was falling from the ceiling. (Though this is not best practice in the vicinity of jet engines.) Australian flags – and dingos, probably – were distributed among the crowd. "We are going to Australia!" repeated Oprah, over and over. And finally their designated pilot, John Travolta, who has been voted the show's most popular guest, stepped out of the plane in his flying uniform and saluted everything. (Do airline pilots salute people? Who cares?) It was like the second coming of a dimpled messiah.

In truth, Oprah's audience had good reason to expect something special. They knew that they had been selected as the show's 300 most loyal viewers. As such, they will also have known about their host's taste for grand gestures. Last season had begun with 21,000 people performing a synchronised dance in praise of the programme's longevity. While in September 2004, Oprah had announced that all 276 women in the crowd, who had been chosen as especially deserving cases, would be given a Pontiac G6 car, a gift that cost General Motors $7m (£4.5m). (And also turned out to cost each recipient $7,000 in tax.)

"Everyone at Tourism Australia", of course, will be picking up the tab for Monday's stunt. In total, the cost of flying Oprah's audience of 300 people to Sydney in December, and then feeding, boarding and entertaining them for eight days, has been put at more than AU$3m (£1.8m), all of it to be borne by the Australian public.

Wary of a potential backlash, the country's tourism minister, Martin Ferguson, has insisted that Oprah "has the potential to lift Australia's profile as a premier tourist destination". A previous minister, John Brown, was blunter. "We spent hundreds of millions of dollars over 30 years without much effect, I must say that honestly," he said. "The publicity that Oprah will bring to Australia around the world is something you couldn't buy." Not for less than AU$3m, anyway.

When The Oprah Winfrey Show finally concludes, on 9 September next year, Oprah herself will not be disappearing with it. Indeed, she has already announced plans to launch an entire television network. Nevertheless, that last show does promise to be something truly terrifying. One can only guess at what sponsored munificence the programme makers have in mind. Whatever it turns out to be, my guess is that Kimberly-Clark, the owners of Kleenex, will do rather well out of it.

And now meet the pilot . . .

Certainly the strangest detail of Oprah Winfrey's big adventure is that John Travolta – you know, the actor – will be flying the plane. "Maybe all of you don't know this," Oprah explained to her reeling audience, "but John Travolta is actually a real Qantas airline pilot." And it is true, just. Travolta is an enthusiastic flyer of many years' standing, who owns five aircraft, including a Boeing 707, which he keeps parked outside his house. And as part of his role as an "ambassador-at-large" for Qantas, he maintains a qualification to fly a jumbo jet. In this position, he engages in many of the typical duties of an airline pilot, such as appearing on Oprah, posing with girls in short skirts, waving the chequered flag at the Australian Grand Prix, and sometimes flying planes.