Norwegian is doing this for purely economic reasons; are there any American carriers in similarly deep financial strife to Norwegian?
Many of the other big, "traditional" national carriers (including American, Delta, and United) have been through Chapter 11 once. That's not really "trading in the state semi-permanently", though; none of the surviving big-name carriers have been through Chapter 11 more than once, and all are currently out of it.
https://en.wikipedia.org/wiki/List_of_airline_bankruptcies_i...