Wang Zhenghua, 71, who emerged as China's newest aviation billionaire after his Spring Airlines floated in January, is a notoriously frugal man. The founder, president and quarter owner of what is now Asia's biggest budget carrier by market value, Wang still chooses to live on a budget himself. In the hallway leading to his office that is less than 10 square metres, only the first and the last of the six lights were turned on. "Cost saving is any time," he said proudly. Wang, known for travelling with his rice cooker and instant noodles, is no stranger to no-frills. The airline he created 10 years ago - initially for charter services for his travel agency business - on Thursday posted net profit of 254 million yuan (HK$322 million) for the first quarter of this year, up 46.4 per cent year on year. Wang said he did not expect Spring's share price to soar by six times over the past three months as analysts rushed to endorse the airline's unique business model in which Spring Tour International, the travel agency associate, feeds a steady traffic flow. The immense potential of China's low-cost travel market has also led analysts to forecast Spring Airlines' net profit to at least double by the end of next year from 884 million yuan last year. With a net margin of 20.8 per cent reported for last year, not only does Spring outshine all legacy carriers in Asia on razor-thin margins, its return on equity of 28.1 per cent is almost twice as high as the figures at low-cost giants Southwest Airlines in the US and Ryanair in Europe. But Wang remains sober and dismissive of any such comparisons: "I know what we really are. We've only got 51 planes," he said. He is equally frank about the larger-than-expected losses and difficulties at Spring's Japanese subsidiary, Spring Japan, which is still awaiting permission from the Japanese government to fly internationally since operating domestically from last August. It was hoped that the Tokyo-based airline, currently with a fleet of three Boeing B737s, could start flying to China this month using Japanese traffic rights, allowing Spring to bypass Chinese traffic rights restrictions. While Japan is already Spring's largest overseas destination with flights to Osaka, Sapporo, Ibaraki and Saga, Spring could not get permission from the Civil Aviation Administration of China to fly to Tokyo - with all quota taken up by China's legacy carriers. "We had thought it would be difficult but not this difficult," Wang said. Both the cultural and political obstacles involved in a Chinese brand's operation in Japan and in obtaining the international flight permit have far exceeded his expectations, he said. "In China, Spring Airlines had turned profitable after we spent just 40 million yuan … I thought five or six times that amount of initial investment would be enough for Spring Japan, taking into account higher labour costs. I really did not expect 10 times that to be still not enough." Spring Japan's loss widened to 253 million yuan at the end of 2014 from 66 million yuan in 2013, according to Spring's annual report. Wang admitted the Japanese shareholders, which include venture capital firm Skystar Financial Management and travel agency JTB, are "very worried". After a capital injection of 1.8 billion yen (HK$2.28 billion) in December 2014, Spring has sunk 3.8 billion yen into the Japanese venture, making it now a 48 per cent stakeholder. But Wang said he remains unfazed and is still trying to gain permission for Spring Japan to fly to China and Korea because of his belief in the untapped market potential for air travel between the three closely linked neighbours in a love-hate relationship. "You have to understand what the market needs and what is your edge; that is where you find the blue ocean," Wang said. "I know my planes are good for destinations no further than four to five hours. Draw a circle within that range and I think Japan and Korea best lend themselves to our cost-conscious and group travellers," he said. Spring currently flies 36 international routes and 94 domestic ones from its bases of Shanghai, Shenyang, Shijiazhuang and Shenzhen. Wang said Spring will have 100 planes by 2018 and further grow its international business - which accounted for 20 per cent of its revenue passenger kilometres in the first quarter of the year, an aggressive expansion of 171 per cent year on year. While Spring is adding a Chengdu-Bangkok service this month, Southeast Asia, where AirAsia and other low-cost carriers already dominate, is not a priority for Spring, Wang said. "In my 20 years in the mainland tourism business, I saw at first Hong Kong and Macau were the hottest; five or six years later it was Southeast Asia, then about four years ago it was Taiwan. Now I believe it should be Japan and Korea," he said.