China's Spring Airlines plans to raise up to 4.5 billion yuan ($724.7 million) in private share placements to fund internet projects and the purchase of new aircraft, it said.

The budget carrier, which also announced a significant jump in half-year earnings, said it intends to buy 21 Airbus A320 jets and will stick to its Northeast Asian strategy, seeking improved penetration into markets such as Japan, South Korea and Taiwan.

First-half net earnings rose by between 130 percent and 150 percent from the 270.8 million yuan achieved in the same period last year, the company said, citing lower fuel prices and growing passenger numbers.

The company had halted trading in its shares this month, pending the private placement announcement.

Spring Airlines is not alone in stepping up efforts to tap China's booming air travel market. Shenzhen Airlines has struck a $4.3 billion deal to buy 46 Boeing 737s, parent Air China said in June, as the group looks to fly more routes.