jwitkin wrote:OK, thanks. I guess my question was about how iMessage works - if he sends an iMessage while on wi-fi, and the recipient is not an iPhone customer, does the Apple server tell my son's phone in France to try to send an SMS message, or does the Apple server itself originate the SMS? I gather you are implying that it would come from my son's phone, and would therefore fail in airplane mode.?
The message app on the phone determines which service (iMessage or SMS) to use. If the recipient is not an iPhone customer or other Apple device, the message app won't even attempt to send via iMessage. In this case, it would attempt to send via SMS and fail since the phone is in airplane mode.