Possible Clues:

• Rough way to bring a plane down (2 words)
• Pilot's emergency procedure
• Tense moment for a pilot
• Coming down due to an unexpected bug perhaps fall asleep by the top of the stairs
• Run into upstairs? That's one way of coming down with a bump!
• Tough way for a plane to come down to earth (2 words)
• For this reason we all have to tighten our belts for accident at top of stairs
• To go to sleep mid-flight could cause an emergency
• An emergency for Jumbo, say, caught taking risks by top of stairs
• Emergency descent