During my process I referenced this site often and found the other reviews to be very helpful. I'm going to share my own experience, and add a few answers to questions I had which WEREN'T answered here, because so many others were.
I applied probably around late November, early December, and on December 17th or so I received an e-mail to complete their online video interview. These questions are pretty basic customer service questions e.g. "What was the best customer service you ever received?" and "Would you be willing to relocate for the job?"
I didn't hear back until December 30th, but keep in mind the Holidays were in that time lapse, so it probably won't be as long for others. On the 30th I got an invitation to answer a few more questions and was told I was "moving forward" in the process. Now, I responded immediately, however, days later I still had not heard anything back.
On January 10th, a little less than two weeks later, I called them and asked to make sure I had done everything, etc. In response I was transferred over to someone who scheduled me for a face to face interview.
My number one emphasis here is going to be don't be afraid to call if it's been a while or if you have questions. Talent Services is really friendly and generally it'll work in your favor. Or it did for me anyhow.
I scheduled my group interview for early February but was not sure of any flight details. They WILL pay for your flight (obviously) and they will contact you with flight information, though it will likely be sort-of last minute, as they have to get you in those left over seats on your flight.
The group interview is exactly as others have described here:
First you get a sheet of paper where you fill out a bit of information and answer a pretty basic customer service question.
Second you go into another room and sit in groups of about five, then do a group activity where you are obviously being judged by your ability to work in a group. Just be friendly, outgoing and outspoken, but not overbearing, and have fun with it. I think what they want to see most is that you are comfortable listening as much as speaking and working with others, as opposed to how much of a leader you can be.
Next you have a group interview. In different groups (also of five) you will be interviewed by two people, once again they are pretty basic customer service questions, but some that are more to explore your personality than your customer service skills. My advice here is to make sure you're heard but do not speak over any other candidates, the more you get along with the others the more relaxed you will all be, and of course it'll make you all look good.
There is one exercise here where they give everyone individual questions on cards that they hand you face-down. This one is clearly for an individual response with no influence by the others. None of these questions are particularly hard (that I saw). Examples were "What experience in your life do you think has best prepared you for the Flight Attendant position?" and "Do you think Social Media has had a positive or negative influence on the world?" (I recommend tying this one back to business purposes and positive customer feedback).
After about five questions or so, we were all taken back to the previous room and given a presentation on the demands and benefits of the flight attendant job.
After about thirty minutes, employees begin entering and taking hopefuls one by one for "one on one" interviews. At this point, they generally know whether or not you'll be moving on and one of two things will happen:
1. You will be given a brief "one on one" where they ask basic questions, if they ask anything, then ask if you have any questions for them.
2. You are taken to an actual one on one with more questions about you and about the job either before or after you are fingerprinted and given a basic "reach test" to be sure you can perform basic job functions at certain heights.
From here everyone is sent back to the airport for their returning flights.
In some instances people heard back within a day, for me it was around 48 hours before I received DOT forms. They are a rather simple employment history/ background check form which you must complete and fax back to them within 3 days.
Less than a week later I received an e-mail with a conditional job offer inside. I accepted immediately and a day later received the e-mail to set up my medical tests. Those are going to be in just under a month.