Mint Explainer | What really went haywire at IndiGo?

Crew shortages due to new duty-time rules, technical breakdowns at key airports, and heavy winter congestion have precipitated the crisis, according to the airline.

Mint explains why IndiGo has been hit the hardest.

What are the new flight duty-time limitations?

India's second and final phase of Flight Duty Time Limitations (FDTL), designed to reduce pilot fatigue and improve safety, took effect on 1 November, requiring overhauls to duty schedules, night-landing plans, and weekly rest charts.

For instance, pilots’ weekly rest period has been increased from 36 hours to 48 hours. Night duty hours have been redefined as the period between 0000 and 0600 hours—an extension of one hour—and the permitted number of landings during this window has been reduced from six to two. Additionally, pilots can now be rostered for no more than two consecutive night duties.

This means airlines need more pilots and a mandatory reset of their duty rosters, said captain Shakti Lumba, an aviation expert and a former IndiGo employee.

Why do pilot fatigue and FDTL norms matter?

The revision of the FDTL norms followed a DGCA audit that found many airlines were struggling with pilot fatigue—physical and mental exhaustion caused by factors such as sleep deprivation, long hours, irregular schedules, and circadian-rhythm disruptions from time-zone changes. In aviation, this is a critical concern because it can affect flight safety, operational efficiency, productivity, and pilots’ health.

The civil aviation regulator collected and analyzed extensive numbers of pilot rosters and fatigue reports submitted by airline operators and released the draft FDTL regulations in January 2024. The revised FDTL regulations were initially scheduled for full implementation by 1 June 2024, but were subsequently deferred.

Have the limitations come as a bolt from the blue?

No. These new rules were initially planned to be implemented from June 2024, but faced pushback from IndiGo and other Indian airlines, and the rollout was delayed. The airlines’ primary argument was that the new norms would require them to increase crew strength considerably, and they wanted the implementation to be done in a step-by-step manner over an extended period.

However, the new norms were implemented this year following a directive from the Delhi high court. They were rolled out in two phases. In the first phase, in July, 15 clauses, including those on weekly rest norms and flying hours, were implemented. The remaining seven provisions, relating to night duty and nighttime landings, were deferred to November to give airlines time to adjust.

During the drafting stage of these regulations, airlines had raised objections and were already aware of the additional hiring they would need to undertake. In fact, since the first phase of the FDTL norms was already in force, airlines such as IndiGo can't excuse themselves by saying they were unaware of these rules or their potential impact, said Mark D. Martin, chief executive of Martin Consulting and an aviation safety expert.

Why is IndiGo in the news, and not others?

Considering the scale and size of IndiGo's operations, the impact is relatively higher. The airline has over 2,300 daily departures, more than double those of its closest competitor, the Air India Group, which has approximately 1,000 departures.

Of the nearly 1,000 domestic routes, IndiGo operates about 600, according to analysts at stockbroker Anand Rathi. The brokerage estimates 87% of the country’s population is within 100 kilometres of an IndiGo-served airport, leading to two-thirds of the airline’s capacity connecting to non-metro cities. Hence, it has a vast matrix of connections, thereby making any duty reshuffling difficult.

IndiGo's network efficiency also depends on maximizing crew hours and minimizing downtime. Once the duty-time limits tightened, gaps opened almost immediately.

Additionally, compared to IndiGo, other airlines such as Air India and Akasa operate fewer night sectors. IndiGo runs many high-frequency overnight services. The cap on night landings significantly reduced the number of flights a single crew pairing could operate legally.

Simply put, IndiGo overlooked warning signs and failed to reset the duty roster. In fact, it wouldn't be surprising if it thought the DGCA would extend the dates again, and now maybe they are trying to create pressure on the regulator to relax these norms, captain Lumba said.

Other airlines, such as Akasa, mentioned in November that new crew rostering norms would impact schedules, and on-time performance would be affected.

When is the situation expected to improve?

IndiGo, on 3 December, said it would take around 48 hours to put things back in order and would employ a calibrated approach. Typically, this means there will be cancellations on select, less popular routes. IndiGo may operate fewer flights than initially planned in its winter schedule, at least for some time.

Its winter schedule had 15,014 weekly departures, as approved by the civil aviation regulator. But even on Wednesday, 4 December, there were a substantial number of flight cancellations and delays.

The regulator has also stepped in and is investigating the matter. It is seeking an explanation from the airline, especially on the corrective measures that it intends to put in place. Details of these measures are yet to be made public.