"We were about to pull away from the gate, and the flight attendant said sir, here is the rest of your boarding pass and handed me a white piece of paper," Mr Stratton told Fox 10.
"Well, I didn't really know what to think. I went up to her and said 'ma'am this wasn't intended for me'. And she just said 'oh god', and that was it."
A Frontier Airlines spokesperson said: "The note was handed to another customer instead of the person it was intended for after the customer changed seats on the plane."
However, Mr Stratton says that's not true, as shown by his boarding pass.
"Those are the seats we were assigned; those are the seats we sat in. I can't imagine it's very easy just to change seats, let alone with someone who is assigned a specific seat for safety purposes," he said.
- news.com.au