I had the same problem with my HP laptop with a Ralink RT3290 wireless adapter.
I was able to solve the problem by doing the following:
Open Network and Sharing Center
Click Change Adapter Settings
Right-click the wireless network icon, and select Properties
Click the Configure... button for the wireless adapter at the top
Click the Advanced tab, click the Radio On/Off property, and change the value to Enable
Close all the windows.
Now the wireless function key should switch between airplane mode and showing the wireless networks.