All their children have 'flown the coop'. [=have moved away from home]
Her books are filled with abstract ideas and 'high-flown' language.
In the morning the suspect had 'flown the coop'.
(..) - Mr. President, please. Sir! Sir! I need an answer. I'm not doing this, guys. Abort mission. Pull out! Abort! Abort! Abort! No! They have flown over the White House. It is an unbelievable moment down here. And Emily Cale is undoubtedly a beautiful hero of the day. (..)2013 White House Down