Possible Clues:

• It's terrifying if it won't open
• It opens during the fall
• Drop equipment
• Equipment that can always let you down
• Essential skydiving kit
• You'd want me in an emergency? I'd let you down!
• Aircraft's emergency device
• Light fixture that helps passengers leaving the plane
• We hope it brings us down to earth
• We may hear soldier bring down retardant from plane