Sorry if this is a bit off-topic, but it happened to me a few days ago.

I was going LHR-ORD on UA. I was seated in Business Class, in the first row of the cabin. I was one of the first on the flight and need to use the lav. So now others were coming on and instead of using the lav in Business, which is at the very end of the cabin (to avoid swimming upstream when finished), I decided to use the lav in F (only two rows away).

I was waiting for the lav when one of the FA's asked me if I needed anything. I told her what I wanted to do. She told me that I should use the lav in Business. I told her why I really didn't want to (she could see all the people boarding and the congestion). She then told me it was a Federal Rule that I could only use the lav in my ticketed cabin.

I told her that the plane was still on the ground, door wide open, not moving and pax were still boarding. If it were flying, I certainly wouldn't do it (and I do respect that rule and don't). She insisted that it was the rule. I challenged her on it.

She then said "Do you want me to get the Captain involded?" I said sure, go for it.

Captain comes out and we begin our discussion. He looked and said the lav was occupied (which I knew). FA continues to rant. Captain turns around and looks at lav again. He says "It's free now, go ahead and use it."

Unbelievable.