source:[1] Spirit Airlines Is Struggling, and Rivals Smell Blood (https://finance.yahoo.com/m/71118807-9abc-3d7 ...)[2] Chapter 11 redux: Spirit Airlines' quest for financial stability - Travel Weekly (https://vertexaisearch.cloud.google.com/groun ...)[3] Frontier Airlines' Stock Soars as Spirit's Struggles Create Opportunities (https://vertexaisearch.cloud.google.com/groun ...)