When you lose something on a JetBlue plane, you can contact JetBlue Lost and Found department. To report a lost item on JetBlue flights, visit their official website and fill out an online lost item report with your contact information, flight details, and a description of the lost item. If there is no online form, contact JetBlue's customer service directly. Remember to check with the airport's Lost and Found and follow up with JetBlue periodically.