According to Alibaba, China's biggest online shopping site, each of the 13 main courier companies in China has invested at least 1 billion yuan to upgrade their infrastructure. As many as 150 warehouses have been built or expanded.

To handle the surging number of deliveries expected on the date, other Chinese courier companies began looking early this year to expand their air services.

Shanghai-based STO Express Co said it planned to set up an air cargo unit by acquiring six to eight aircraft next year as the number of parcels shipped during the festival continues to climb.

"More than 20 percent of our parcels are now being delivered by air," said Shen Tao, the company's public relations officer. "To tap the booming market, the only sensible move is to invest in our own air fleet."

A Beijing recruiting agency said it was getting a lot of business from express firms needing delivery people.

Delivery services have become the latest frontier in an e-commerce battlefield as online retailers compete to make the customer experience as cheap and easy as possible, experts said.

"Last year, the battle over double 11 began with the competition for retailers. This year it is the logistics," said Liu Yong, a courier with more than five years of working experience.

Liu said he still had another 70 parcels to deliver in the afternoon. He was lucky to get 10 minutes for lunch.

"I used to deliver 80 to 100 parcels on a normal day, but a peak day like this, I double my workload," he said.

Last year, Alibaba generated 19.1 billion yuan in sales during the double 11 promotions, almost twice the revenue generated by the US' post-Thanksgiving Cyber Monday event.

The company said it was expecting to rake in 30 billion yuan in sales for the day this year.