A Beijing court has ruled in favour of a lawyer in his lawsuit against the Ministry of Finance, and ordered it to disclose publicly information it claimed were "state secrets".
Lawyers hailed the verdict as a victory for transparency and the rule of law on the mainland.
Starting in May of last year, the Finance Ministry has tacked 50 yuan (HK$63) on to the price of domestic air tickets and 90 yuan to international ones, with the money going to a government aviation development fund, Xinhua reported.
Wang Luchun felt the extra charge was unfair and, the following month, requested as a private citizen that the Finance Ministry make public its reasons for the fees and how they were used in the development fund, according to the Xinhua report.
In June 2012, the ministry wrote him a letter denying his request, saying the information was a state secret. Wang took the ministry to court.
He said he believed that the government should treat public disclosure of official information as the norm in light of a law on the matter enacted in 2008.
He felt there should be a "clear legal basis to justify the classification of information as state secrets", Xinhua said.
The Beijing First Intermediate Court last week ruled that the ministry lacked sufficient evidence to prove the information amounted to state secrets.
The court ordered it to publicise details on the fees and its use for the aviation development fund, as Wang had requested.
"The verdict shows the Chinese court is demanding government bodies to be more transparent and accountable," said a lawyer at an international law firm. "Increasingly, more litigation is brought against Chinese government bodies.
"It's an evolution of Chinese society," the lawyer added.
A managing partner at a US law firm said: "This can be a sign that the Chinese government is trying to emphasise that nobody is above the law.
"Transparency, accountability to the law and the rule of law are on the rise in China. This trend is going to continue."
The US Securities and Exchange Commission had been trying to obtain information on Chinese companies listed in the United States, as part of its fraud investigations into some US-listed Chinese firms.
Previously, the SEC could not access certain corporate information on the mainland as it fell under the category of state secrets. The Chinese and US governments resolved this stand-off with an agreement reached in May, which gave US regulators limited access to Chinese companies' documents.