One of the Pratt and Whitney engines of an IndiGo A320neo plane bound for Pune, stalled mid-air, forcing it to return to Kolkata Airport on Wednesday. This the fourth such incident involving PW engines at the low-cost carrier in a week, from October 24 to 26, IndiGo had three in-flight PW engine shutdowns. The engine stalled while the flight 6E-862 was gaining altitude and at around 9,000 feet, and pilot observed an engine #1 caution message. Following the incident, The Directorate General of Civil Aviation (DGCA) directed the low-cost carrier on Monday to replace the 29 Pratt and Whitney (P&W) 1100 series engines, which have operated more than 3,000 hours, on 16 A320neo aircraft, within the next 15 days. According to DGCA the major issues that rose following the induction of P&W engine powered A320 Neo aircraft included ‘combustion chamber distress (Block B and Block C)’, ‘N2 transient vibration’, ‘Low Pressure Turbine (LPT) failure’, ‘gear box failure’ and ‘#3 Bearing Pre Mod and Post Mod failures’. DGCA also instructed GoAir on Tuesday, to replace the PW engines on its 13 A320neo aircraft. IndiGo is the largest airline in India, which operates 218 Airbus A320 family Aircraft including 97 A320neo.