I don't know how long the free service will last
Turkish Airlines welcomes you on board
You are one of the first passengers to be able to experience the new in-flight HotSpot service. For a limited time, Turkish Airlines passengers will be able to enjoy the Internet service free of charge. So go ahead, surf away or send and receive emails at 10,000 metres.
Service is provided by T-Mobile. For example, when I go to Yahoo, it thinks that I'm located in Germany.
Here's some info on bandwidth available:
How much bandwidth is available on a single aircraft and what is the average speed for data transfer?
With the roll-out of Planet, each aircraft will provide an incoming transfer capacity (download) of approximately 5 Mbps and an outgoing transfer capacity of approximately 1 Mbps (upload). The available bandwidth is shared by all Planet-users onboard, which means that the actual speed depends on the actual number of users, as is the case with common ground hotspots. Assuming average internet usage, the speed will be the same as if you were at a public hotspot on the ground.
The 24-hour pass seems to indicate that it could be used for multiple flights, but again since it's free on the flight I'm on I didn't need to go through this part:
24 Hours
Pass Sky
Usable up to 24 hours after the first login.
No volume limit
No contract