If AirPlay is working, but then suddenly disconnects and you lose the AirPlay icon, this is common for me and the only thing that helps is to turn off the cellular aspect of the iPhone.
If this happens to you then put the iPhone into Airplane mode and turn wi-fi back on. For me, AirPlay will then will reliably stay connected, which leads me to believe that there is some sort of RF interference between the cellular and wi-fi radios, or perhaps some sort of software conflict between these two functions. I live in a remote area where cell reception is not very good, so my condition may be worse than most because of the increased cellular radio output trying to keep (or find) a connection.
But if this does not bring back the AirPlay icon, try a power OFF/ON of the iPhone, or a reset. A "hard" drop out of AirPlay, where it won't come back even with cellular off and wi-fi on, rarely happens to me but a power cycle has always brought the AirPlay icon back, but I always have to have it in Airplane mode for it to stay connected.
Currently Being ModeratedAug 10, 2011 8:15 PM (in response to rockmyplimsoul)
Thank you guys. The airplane mode didn't work, but powering the iPhone off and on did restore the airplay icon for now. We'll see how long it lasts. Your suggestions are much appreciated.
Currently Being ModeratedJul 10, 2013 12:51 PM (in response to rockmyplimsoul)
Rebooted the router | put iPhone into Airplane mode and then switched on WiFi again - go to iTunes and AirPlay icon is back.
Music is playing again through external Bose Air Play speaker.
Thank you RockMyPlimsoul......
Currently Being ModeratedJul 10, 2013 12:58 PM (in response to IT Supporter)
Glad it worked, for some reason this only affects the iPhone 4 in our house, not iPhone 4S or 5. If you don't want to switch to Airplane mode, another thing you can do is turn off Bluetooth on the iPhone and Airplay seems to be more stable.
Currently Being ModeratedJul 10, 2013 1:21 PM (in response to rockmyplimsoul)
It worked fine and I am using iPhone 4s - I had switched off the bluetooth, which will be annoying because my Macbook Pro has a bluetooth Magic Mouse so will have to do this also to play music that way, but I am now listening to Dark Side of the Moon from my iPhone with a chilled glass of white wine.