Which airline has the lowest customer satisfaction? Spirit Airlines ranked dead last in the latest travel report from the American Customer Satisfaction Index (ACSI). With a score of 54, Spirit dethroned United Airlines as the lowest-ranking carrier on the index. Spirit was added to the list for the first time this year. JetBlue Airways claimed the top spot as the most satisfying airline with a score of 81, a 3% increase from 2014, according to the ACSI Travel Report 2015.