My Grandpa's favorite "dumb blonde" joke.

A blonde is on an airplane to Chicago and gets up from her seat in coach and goes into the first class cabin and sits down.

The flight attendant goes up to the blonde and politely tells her that she does not have a first class ticket and must go back to coach. The blonde refuses and says , "I'm blonde, I'm beautiful, I am going to Chicago, and I am staying right here."

After repeated attempts and no success at convincing the woman to move, the flight attendant goes into the cockpit and informs the pilot and co-pilot that there's a blonde bimbo sitting in first class who refuses to go back to her proper seat. The co-pilot goes back to the woman and explains why she needs to move, but once again the woman replies by saying, "I'm blonde, I'm beautiful, I'm going to Chicago and I'm staying right here."

The co-pilot returns to the cockpit and suggests that perhaps they should have the arrival gate call the police and have the woman arrested when they land. The pilot says, "you say she's blonde? I'll handle this. I'm married to a blonde. I speak blonde." He goes back to the woman and whispers quietly in her ear, and she says, "Oh, I'm sorry," then quickly moves back to her seat in coach.

The flight attendant and co-pilot are amazed and ask him what he said to get her to move back to economy without causing any fuss.

"I told her first class isn't going to Chicago."

edit: Consistency. Apparently, just typing out this joke gives you 'dumb blonde syndrome'.