How to fly free, forever (hint: put US$170 million on your AmEx)

Chinese billionaire Liu Yiqian, who doesn't exactly struggle to afford a plane ticket, can now likely fly free, in first class, with his whole family, anywhere in the world, for the rest of his life.

All because he bought a painting.

Liu was the winning bidder for Amedeo Modigliani's Reclining Nude at a Christie's auction this month — offering US$170.4 million — and when the sale closes he'll be putting it on his American Express card.

Liu, a high-profile collector of Chinese antiquities and art, has used his AmEx in the past when he's won art auctions. He put a US$36 million tea cup from the Ming Dynasty on his AmEx last year, according to reports, and put other artifacts on his card this year. He and his wife said they plan on using their American Express card to pay for the Modigliani, according to news reports after the sale.

American Express will not confirm Liu Yiqian's Modigliani purchase, or say if it would be the biggest ever on their cards, citing privacy reasons. But it can be done.

“In theory, it's possible to put a (US$170 million purchase) on an American Express card,” said American Express spokeswoman Elizabeth Crosta. “It is based on our relationship with that individual card member and these decisions are made on a case-by-case basis, based on our knowledge of their spending patterns.”

Liu has an American Express Centurion Card, also known as the AmEx “black card,” an invitation-only card that is given only to AmEx's biggest spending clients. The card has no official credit limit — and it earns points, just like most of the cards non-billionaires carry around.