An SF Express (Group) Co cargo plane is loaded at an airport in Nantong , Jiangsu province. Express delivery companies are gearing up for the expected online shopping frenzy on Nov 11. [Photo / China Daily]

In the run-up to Nov 11, the country's biggest online shopping day of the year, couriers across China are adding to their transportation fleets and employing "big data" analysis.

The Nov 11 shopping festival, launched by e-commerce giant Alibaba Group Holding Ltd five years ago, has mushroomed into an annual shopping frenzy for millions of online bargain hunters.

More than 20,000 vendors on Alibaba's sites - Tmall and Taobao - have pledged to knock 50 percent off full-priced items on Nov 11.

According to consultancy Bain & Co, it's a day when more people visit the most popular e-commerce sites than the entire population of Brazil.

Bain has forecast that China will overtake the United States as the world's top e-commerce market this year.

The group set a record of 19.1 billion yuan ($3.13 billion) in one-day sales last year. But the sheer volume of orders at times overwhelmed the nation's courier companies and delayed deliveries.

This year, express delivery companies aim to optimize their services by chartering aircraft to serve high-volume areas, among other tactics.

More than 100 cargo jets have been leased by major couriers, according to a statement from Alibaba.

SF Express (Group) Co Ltd, the first privately run courier in China to have its own air fleet, will deploy 31 cargo planes at the delivery peak.

Its competito rs plan similar actions. For example, YTO Express (Logistics ) Co Ltd will run two Boeing 737 cargo planes on the Beijing -Shenzhen route, according to a company announcement. The goal is to move packages from North China to South and Southwest China within 24 hours.