Travel agencies, hotels, airlines and even online vendors are cashing in on the longest solar eclipse of the 21st century, which will pass across China next Wednesday.

The July 22 eclipse, which will last up to six minutes, the longest until the year 2132, has become the promotional tag line for the tourism industry in cities along the Yangtze River, including Shanghai, Suzhou and Wuhan.

"It is a perfect pitch for us. All 50 star hotels in downtown Suzhou have prepared free special glasses for astronomy lovers. The hotel room occupancy rate will definitely go up," said Wu Min with the marketing department of Suzhou Tourism Bureau.

Because of the global economic meltdown, most star hotels in Suzhou of Jiangsu province have seen more than half of the rooms remain empty, she said.

But the eclipse will bring an estimated 10,000 overseas tourists and nearly 100,000 domestic tourists to Suzhou, she said.

"Reservations for hotel rooms on July 21 and 22 have been very brisk. The earliest clients called at the end of last year to book rooms," she said.

Hanting Inn & Hotels, a business hotel chain, also said its hotels in Shanghai, Wuhan, and Chengdu received 20 percent more bookings than the same period last year because of the eclipse.

Even train tickets are now difficult to buy.

"All train tickets from Beijing to Shanghai and Hangzhou on July 21 have been sold out," said Beijinger Yan Yan, who planned to watch the eclipse with four friends.

Though they began to plan last year, the factor of uncertain weather made them miss the chance to buy train tickets.

"Now we changed our destination to Putuo Mountain (in Zhejiang province). Though the air ticket to Ningbo will be full price, this is worthwhile because the most important thing for watching the eclipse is no clouds in the sky," she said.