Possible Clues:

• Domestic flight
• Flight path ...
• It's all up in flight
• Group of joined locks on a canal
• Steps one takes to get to the next level
• Situation of flight - rumpus about a piece of luggage coming later
• Connector of stories
• Sounds as if one must look hard over the box on the way up
• See 4
• Position beneath area in prison - exited via this?