Dense fog blanketed Delhi on Friday morning, forcing cancellation of more than 150 flights at Indira Gandhi International Airport and significantly disrupting travel across northern India. Flight operations have been conducted under CAT III procedures since 9:00 PM Thursday to ensure safety amid extremely low visibility conditions. Airport authorities confirmed that ground teams are coordinating closely with all stakeholders to assist stranded passengers across terminals. "Dense fog is impacting flight schedules, and operations are currently under CAT III conditions. For real-time flight updates, passengers are advised to contact their respective airlines. We regret the inconvenience caused and appreciate your understanding," an official statement said. CAT III is a category of the Instrument Landing System that permits aircraft to land in extremely low visibility by allowing lower decision heights. In some cases, it enables near zero-visibility landings, though this requires advanced aircraft equipment and specialized pilot training. IndiGo issued a travel advisory acknowledging the seasonal disruption. "Early-morning fog in Delhi and across parts of northern India is reducing visibility and disrupting flight operations. Customers travelling in the early hours may experience delays or revised timings," the airline posted on X. Delhi's Air Quality Index plunged to 387 at 7:05 AM Friday, deteriorating from Thursday's rolling average of 373, according to Central Pollution Control Board data. Dense fog has impacted flight operations throughout the week, with other parts of North India also reporting similar conditions affecting arrivals and departures.