Determine the type of adaptor you require
First of all you need to call your air line help-line or simply take information from travel agents that what type of ports they use. Some airline uses AC ports and some DC ports. In case your airline have DC ports, you can go directly to step 4. You don’t need to buy any adaptor or hardware.
If they have AC ports in their flights then you need to proceed towards the next step.
Place DC adaptor of your iPhone to the DC to AC adapter
After figuring out your airline has AC ports in your flight, insert the DC adaptor of your iPhone 3G into the DC to AC adapter.
Join adapter to other side of AC adaptor
Next you need to join the adaptor to the opposite end of the AC adapter.
Remember if no adapter is needed then you can leap over this step.
Join the adapter to the adapter on plane
In the end, simply connect the adapter to the one present in your flight. The Adapter in your flight can be place on your armrests, on the back of the seat in front of you. Plane adapter can also be located on the side of your seat.