JetBlue doesn't overbook, but they do swap A320 for A321 which have 50 fewer seats, fairly randomly, which leads to a lot of IDBs (you can ask for volunteers an

JetBlue doesn't overbook, but they do swap A320 for A321 which have 50 fewer seats, fairly randomly, which leads to a lot of IDBs (you can ask for volunteers and get them when it's 1-5 people on a 200 person flight; you are probably screwed if you need 50 people on a 250 person flight.)