New Delhi, Dec. 6 -- The civil aviation regulator on Friday gave in to IndiGo's request and granted a one-time exemption from certain crew fatigue rules introduced last month, as India's biggest airline cancelled flights for the fourth day amid an operational meltdown and chaos that has stranded tens of thousands of passengers. The Directorate General of Civil Aviation (DGCA), the regulator, said IndiGo's representations prompted the relaxation. The airline got relief from the provisions limiting pilot duty hours at night, the rules it struggled to adapt to. The airline has said full restoration of operations would take until February 10. The exemption came on the day IndiGo warned of the highest number of cancellations, maintaining it was taking necessary steps to reboot its systems and schedules for progressive improvement. "Short-term proactive cancellations are being made to ease operations, decongest the airports to prepare for starting stronger tomorrow," the airline said in a post on X. IndiGo on Friday cancelled all its flights from Delhi airport until midnight, from Chennai airport till 6pm, at least 104 from Mumbai, 92 from Hyderabad, 102 from Bengaluru, 30 from Goa, and 11 from Jammu. On Thursday, IndiGo cancelled over 400 flights as it admitted to the aviation regulator that the meltdown stemmed from "misjudgment and planning gaps" in adapting to rules it had two years to prepare for. Over 200 flights were cancelled on Tuesday and Wednesday. The crisis underscored the fragility of a business model based on cost optimisation, with minimal operational buffers, and the lack of choice for passengers in the sector, which is largely a duopoly between IndiGo and Air India. IndiGo, which commands 60% of India's domestic market, is the only option in many sectors. P8...