For most of us, it is something that we can only dream about. We can imagine what it might feel like but we cannot hope to ever experience it.
Recently, on SIGForum, I read about the experiences of an extremely fortunate gentleman who got to experience first-hand what a B17 mission feels like.
Here are a few photos of poster windhover's experiences. Please read the thread linked to at the end of the post.
He has very graciously allowed me to share some of his photos with you but to see the whole experience, you will have to read the thread. I highly recommend it.

Crewman "windhover" being kitted out

some equipment being issued to the crewmen

The barracks. You can see a link trainer in the background

being taught the basics of aerial bombing

The aerial gunnery trainer

getting the experience of shooting the .50

The USO girls entertain the troops.

The "Bird"; B17G "nine o nine".

windhover gets to be the ball turret gunner for a while

aircrew meals; SOS


airborne at the tail gunners position.

back on the ground after the mission
Please read the whole story HERE.
Thank you, windhover, for letting me post your photos here. You are an extremely fortunate man and I for one am quite envious of you.
Not only did you get to fly in a B17 but you got to bomb California!

There are more photos, videos and a better explanation at the post linked to (above).