Airplane mode turns off the iPhone radio transmitters to avoid interfering with aircraft operation. In some regions, where allowed by the aircraft operator and applicable laws and regulations, you can turn on Wi-Fi while airplane mode is on, to:
Send and receive email
Browse the Internet
Sync your contacts and calendars over the air
Stream YouTube videos
Get stock quotes
Get map locations
Get weather reports
Purchase music and applications
For more information, see Airplane Mode.