About half of the planes in national flagship carrier Singapore Airlines' fleet are equipped with Wi-Fi services for customers, as are all 12 planes flown by budget subsidiary Scoot.

The two airlines are among the 70-odd air carriers providing passengers with Wi-Fi.

This is typically a paid service, with airlines either using a time-based fee model or charging passengers by how much data they want to consume.

With one in four commercial planes worldwide now offering Wi-Fi access to passengers - and the proportion expected to rise to two in three airplanes by 2025 - here is a look at some regional carriers where being on board does not mean going offline.

1. SINGAPORE AIRLINES

Singapore Airlines offers both volume-based and time-based Wi-Fi services depending on the flight and aircraft in question.

Its volume-based plans start at US$6.99 (S$9.96) for a 15MB plan and can be used only on a single flight segment, so the Internet access does not transfer to connecting flights. Time-based charges start at US$11.95 for an hour.

Customers of local telcos Singtel, StarHub and M1 can also purchase unlimited data on selected aircraft, with prices starting at $25 a day.

2. CATHAY PACIFIC

Hong Kong's Cathay Pacific offers Wi-Fi service on flights aboard the Airbus A350 aircraft.

It charges US$9.95 for one continuous hour of Internet access, US$12.95 for flights less than six hours long and US$19.95 for flights longer than six hours.

3. GARUDA INDONESIA

Garuda's Wi-Fi services, offered on its Boeing 777-300 and Airbus A330-200/300 aircraft, operate on a time-based fee model.

Prices start at US$11.95 for one hour of Internet access. A data cap also applies on Airbus flights, with the first 15 minutes online free.

In-flight Internet is free for passengers flying first class.

4. VIRGIN AUSTRALIA

The Australian air carrier offers free Wi-Fi access on short-haul flights aboard certain Boeing 737-800 and Embraer 190 planes.

It defines international short-haul flights as those between countries in South-east Asia and the Pacific region.

5. CHINA EASTERN AIRLINES

China Eastern Airlines is currently piloting a trial Wi-Fi service on selected intra-China and international routes.

Up to 50 passengers on each of those flights can log on for free if they register in advance on China Eastern's website.

The international flights offering free Wi-Fi access are between Shanghai and New York, Los Angeles, Toronto and Chicago.