Recently on a trip to Shanghai, I was confused to find that as my plane lifted off Melbourne's Tullamarine tarmac, the internet services that I took for granted like Google, Facebook, and Twitter failed to load while WeChat and Weibo were still accessible.

Key points: Australia technically owns the air inside the plane but it's also Chinese territory

Australia technically owns the air inside the plane but it's also Chinese territory Every aircraft has its own "nationality" under the Chicago Convention

Every aircraft has its own "nationality" under the Chicago Convention The Great Fire Wall is comparable to a digital border that China built in 1994-1996

I had been attempting to browse the internet on my China Eastern-Qantas codeshare flight with no success, before I realised the continuous buffering was not due to low signal.

Instead, I had somehow hit the Great Firewall of China while still in Australian airspace. This confused me because my flight — that I booked on the Qantas website — was listed with Wi-Fi services.

Social media like Twitter was blocked. ( ABC News )

As someone born in China before the beginning of internet censorship in the mid '90s, and having become accustomed to unlimited internet access in Australia over the past decade, I felt uneasy about having to face 10 hours without internet — or more specifically, restricted internet.

With a lot of time on my hands to think, the censored internet services over Australia got me thinking: why was my in-flight internet censored in Australian airspace, and which country's laws are in effect when you're inside an aircraft?

'Aircraft part of Chinese territory'

The space inside China Eastern aircrafts is seen as an extension of Chinese territory. ( Flickr: G B_NZ )

The questions sound simple enough, but they actually traverse complex issues of aviation and telecommunications law, as well as individual airline policies — a few fairly dense topics.

Luckily there are some simple ways to explain why Chinese censorship laws can be enforced on a plane flying over Australian territory.

Qantas and China Eastern signed a five-year agreement at Parliament House in late 2014. ( Supplied: Qantas )

According to Jae Woon Lee, an aviation law expert from the Chinese University of Hong Kong (CUHK), the inside of the plane I was travelling on is essentially considered to be "Chinese territory".

He said because China and Australia have both ratified the Tokyo Convention — the international treaty laying out which country's laws apply aboard an aircraft — Chinese laws and regulations were in effect on my flight.

"The Chinese registered aircraft is kind of part of the Chinese territory, conceptually the idea is right," Dr Lee said.

Joseph Wheeler, the principal of the International Aerospace Law and Policy Group, said every aircraft has its own "nationality" under international law.

This means if you're flying on a Chinese plane, the flight is under the authority of their national regulator, the Civil Aviation Administration of China (CAAC).

He said internet regulation aboard the plane — whether it is accessible and what is accessible — was determined by a combination of Chinese laws and policies, as well as the airline's own conditions.

But I bought my tickets from Qantas?

From left to right: China Eastern chairman Liu Shaoyong, Chinese President Xi Jinping, former Australian Prime Minister Tony Abbott and Qantas chief executive Alan Joyce. ( Qantas, supplied )

Qantas and China Eastern signed a five-year partnership agreement at Parliament House in late 2014, in a ceremony attended by former Australian prime minister Tony Abbott and Chinese President Xi Jinping.

How do codeshare flights work? There is one operating carrier (in this case, China Eastern) and one or more marketing carriers that sell the tickets

There is one operating carrier (in this case, China Eastern) and one or more marketing carriers that sell the tickets Marketing carriers like Qantas assign the airline code to the flight

Marketing carriers like Qantas assign the airline code to the flight It enables airlines to coordinate schedules, provide more destinations and cut fares

This agreement led to a codeshare arrangement between the two.

When I booked my flight through the Qantas website, inflight Wi-Fi was advertised on the listing.

The page made it clear that the flight would be operated by China Eastern Airlines, however there was no specific mention of the Wi-Fi services being subject to the Great Firewall of China.

When asked whether customers are made aware that the advertised Wi-Fi would be censored, Qantas said:

"While a customer may book through Qantas.com, it is made clear that the flight is operated by China Eastern … and as such their onboard experience is bound by the condition of carriage of China Eastern."

When asked whether customers on Qantas.com are told specifically what those "conditions of carriage" are, the company said customers are made aware that "product features may vary between aircraft".

It said its a matter for the operating carrier to determine what services are available on board.

China Eastern did not respond to my questions, while a spokesperson for the Australian Competition and Consumer Commission — the authority who granted the Qantas and China Eastern joint operation — said they could not comment on the issue.

China's Great Firewall is getting taller

The Great Firewall first came into effect in the mid 1990s. ( AP: Eranga Jayawardena )

China has always kept a tight grip on what can and cannot be accessed on its internet, and began regulating it almost as soon as it arrived in the country in 1994.

The most notable of these is the system of technology most well-known as the Great Firewall of China, which slows down, analyses and blocks online content from overseas.

Just like my in-flight experience, Chinese netizens cannot access popular Western social media sites and apps, or foreign news outlets like the New York Times.

Jyh-An Lee, an expert on Chinese internet censorship from the CUHK, said the Great Firewall was essentially a digital border.

"Most people would believe that there is no border to the internet," Professor Lee said.

"[But] if you are flying with the state-owned flight company, and if you are using the free Wi-Fi, you are actually subjecting yourself to the extension of the digital border which comes from the Great Firewall."

The Chinese Government introduced and promoted the concept of cyber sovereignty at its World Internet Conference in 2014, before tightening its cyber regulation and cracking down on tools that allow users to get around the Great Firewall last year.

Cyber sovereignty is the idea that states should be able to manage and contain their own internet without external interference.

Chinese businesses expected to 'self-censor'

China's Great Firewall is able to shape users' behaviour in the country and is getting stronger.

While there is no simple explanation as to why China is able to censor Wi-Fi services in Australian airspace, Professor Lee said he wasn't surprised that a Chinese company — especially a state-owned enterprise like China Eastern — would implement self-censorship.

He said there was an expectation from Beijing that companies would self-censor sensitive information and websites even if it wasn't enforced.

Professor Lee added that China's Great Firewall was able to shape users' behaviour in the country and was getting stronger.

Whether that's the case or it's government-enforced censorship, experts say there remains many grey areas on the subject that need to be ironed out.