Spare car key. Spare house key.
Here's my story that explains why I have spare car keys SEWN INTO MY LUGGAGE.
I was in the Rochester NY area on a business trip. After the meeting, I was getting ready to go through security, and I always zip my key ring & phone into my roll-on bag's outside pouch right as I go through security. Of course, no keys in my pocket. Oh boy...my flight is in 1 Hour and 30 minutes.. It's the second-to-last flight home of the day...the last flight is full. So it's the last flight for me.
I call the client - are my keys at their office? Nope.
I call the hotel - did I leave the keys in the hotel? YES!
But the hotel is a 45 minute 1 way drive back. My flight is in one hour 30 minutes...unless I can get a cab to drive really really fast...ugh..not going to happen.
The woman on the phone says, "Well, Joe here can come to the airport with your keys. Joe's a groundskeeper, but he'd be happy to come by. Where should he meet you?"
Joe showed up, I got home, but after that - spare keys are permanently enclosed in my EDC bag, my travel backpack and my roll-on.