Possible Clues:

• A pole vaulter hopes for a safe one
• Takeoff's opposite
• A gap between flights coming down
• It's at end of flight, in two senses
• You reach it going up the stairs or coming down
• At the top of the stairs, and coming down
• It ends a flight (in two ways)
• Not taking off half way up the stairs
• It ends a flight, in two ways
• End of a flight