I used to work at Jetblue. We had a program that allowed flight attendants to sit on the flight deck Jumpseat. It was called an observation ride and they could do it once a year. The problem was some of them would do it 25-30 times a year and the Faa pulled it. So it can be done if all parties agree to the rules. I liked it for the most part. They could only use it if no other pilot (online or off) needed it.