NEW DELHI, India: IndiGo's mass flight cancellations have plunged Indian aviation into a week of turmoil, stranding tens of thousands and sharpening concerns that the country's dependence on a single dominant carrier has become a structural risk.

India's largest airline, with a 65 percent domestic market share, scrapped at least 2,000 flights after failing to anticipate new limits on pilot working hours. The disruption, one of the worst in India's aviation history, upended weddings, holidays, and business travel, with images of lost baggage and crowded terminals circulating widely online.

For nearly two decades, IndiGo has symbolised India's aviation boom and the government's ambition to make air travel accessible to millions. Prime Minister Narendra Modi once said, "Those in slippers should also be seen in aircraft." But the crisis has exposed how dependent the fast-growing market has become on two carriers: IndiGo and Air India.

Rival Air India, which holds 27 percent market share, is contending with an ageing fleet, service complaints, and heightened scrutiny following a June crash that killed 260 people.

IndiGo says operations should stabilise within days, and the government has temporarily relaxed pilot fatigue rules to ease the logjam. The airline has apologised repeatedly but has not detailed the financial impact.

"IndiGo's size has grown to the point where operational setbacks pose systemic risk," said Harsh Vardhan, chairman of Starair Consulting. He warned that trouble at either major carrier could trigger "mayhem in Indian aviation," adding that India must cut jet fuel taxes and encourage more competition.

Although not a formal duopoly, analysts say the combined 92 percent share of IndiGo and the Air India group creates a duopoly-like dynamic. On numerous routes to smaller towns, IndiGo operates as the sole carrier.

"A country cannot grow robustly with duopolies, or effective monopolies, in any sector," wrote Air Deccan founder G.R. Gopinath in the Economic Times.

Several Indian airlines, including Kingfisher, Jet Airways, and Go First, have collapsed in recent years amid high fuel taxes, intense fare wars, and supply-chain constraints. Despite government efforts to expand airports and simplify rules, few new carriers have survived long enough to challenge IndiGo's dominance.

IndiGo, founded in 2006 by Rakesh Gangwal and Rahul Bhatia, has grown to a fleet of over 400 Airbus A320-family aircraft and operates more than 2,000 flights daily under CEO Pieter Elbers. It carried 174 million customers last year and posted US$9 billion in revenue and $807 million in profit.

But the past week has dealt a rare blow to the airline's reputation for punctuality, once a hallmark of its brand. An IndiGo staffer said the situation was "the lowest point in the company's history." Refunds alone stood at $68 million by December 7, with more expected.

IndiGo's on-time performance, 91.4 percent as recently as July, collapsed to 3.7 percent on December 5.

The turmoil has drawn comparisons to Southwest Airlines' 2022 holiday meltdown, which forced 16,900 cancellations and cost the U.S. carrier at least $400 million in revenue.