Two phone screens and an onsite. Overall all questions were fairly practical in that if you have been doing iOS development for a bit, nothing should be too surprising.

Technical Phone Interview by an engineer from the iOS team at Airbnb. The interviewer started out by introducing himself and the work he does at Airbnb. Then we dived right into coding. The coding problem was to implement a view controller that has some UI elements and listens for a gesture recognizer (omits details here). I think the main challenge here is, since the coding is done through an online text editor, there's no auto-complete or anything like that, you need to be very familiar with the syntax and the SDK to be able to implement the whole thing. It's a good idea to talk through your thinking process before and during coding, so that the interviewer would have an easier time understanding your code and the structure of your view controller. The coding took no more than 8-10 mins, then the interviewer asked about the projects that I've done and what would I like to work on if I'm an iOS engineer at Airbnb (followed by some other behavioral questions). The entire phone screen took less than 30 mins. (I received the invitation to an on-site interview a week after the phone screen)