'We're about to crash... no we're not'
 

This is your captain speaking. There is no cause for alarm!
Just beat me to it... Heres the SMH link:
http://www.smh.com.au/travel/travel-...827-13vy1.html

The automatic announcements are actually controlled by cabin crew, not flight crew.

Depending on the aircraft type this could be very easy to do accidently - all you'd need to do it type in the wrong number potentially.

Could also have been a training event where a senior crew member was showing other crew how to operate the system & unfortunately they actually activated it.

Reminds me of this one from last year:

http://news.sky.com/skynews/Home/Wor...15381238?f=rss