Mumbai airport’s T1 redevelopment has triggered a fight over more than capacity.  So, what actually happened?

Mumbai airport runs on two terminals: T1, the ageing domestic terminal at Santa Cruz, and T2, the newer terminal at Sahar, which handles all international traffic and a substantial part of the domestic load. Together, T1 and T2 form Chhatrapati Shivaji Maharaj International Airport and share the same runways, aprons and airside envelope. Closing T1 for redevelopment, therefore, does not merely remove domestic gate capacity, it also reduces the number of aircraft movements the whole airport can handle while the works are in progress. And, as the two terminals sit roughly 4-5 km apart, the constraint runs across the entire airport rather than just at the domestic terminal.

The Mumbai airport concession was awarded in 2006 to a GVK-led consortium, which set up MIAL (Mumbai International Airport Ltd) to hold it. MIAL is now Adani Group-controlled. The concession covers the entire airport, not just T2, which opened in 2014. The OMDA (Operations, Management and Development Agreement) details the development obligations of the operator, including the phased redevelopment of older facilities. T1’s redevelopment is, therefore, squarely within MIAL’s mandate, as part of the concessionaire’s obligatory works.

The current “dispute” is not about whether MIAL is to redevelop T1, but about how it has chosen to manage the capacity fallout.

On that, MIAL says Mumbai airport must shed around five million passengers a year from the Summer 2027 schedule. To absorb the loss, it proposed that airlines cut 33% of their international departures (i.e., 265 of 770 weekly international services) or shift them to Navi Mumbai by the initial deadline of October 25.

Forty-six airlines received this communication. They have objected. The Ministry of Civil Aviation intervened earlier this month and asked MIAL to engage with stakeholders on a mutually agreed transition plan rather than proceeding unilaterally. MIAL has since deferred the shift until the Summer 2027 schedule. A joint working group is to draw up the implementation plan; its follow-up meeting is set for October 28.

The dispute is over the redevelopment of T1, specifically who bears the capacity loss and who decides how to distribute it.

What Are the Airline Operators’ Complaints?

There are three distinct objections, each with a very different legal weight and bearing.

Procedural: The Airline Operators Committee rejected “any unilateral reallocation of traffic, reduction of slots or relocation of international operations without due process”. Airlines say they have not consented to transferring international operations or to any reduction or cancellation of existing slots.

Evidential: Airlines have sought detailed information on terminal capacity, passenger traffic and utilisation, and clarity on the methodology behind the five million figure and the 265-departure figure. This is the strongest objection on record, as it goes to the heart of the claim: MIAL has claimed an airside capacity constraint flowing from the T1 works but has not released publicly the arithmetic that produces the numbers (terminal capacity, passenger traffic and aircraft movement limits). Airlines have questioned the basis for the cut; some commentary goes further, suggesting that T1 itself operates below capacity. This may or may not be a legitimate claim -the utilisation data are not public. But it is precisely the kind of claim MIAL could settle immediately by publishing the numbers. It has not done so to date.

Commercial: Emirates has said plainly that Navi Mumbai “is not ready” for international operations: catering, cargo warehousing and the wider ecosystem are yet to be built out. Air France-KLM has said splitting operations between the two airports “does not make sense”. This is a real objection, but it is a negotiating position rather than a legal one, as an airline’s commercial preference does not by itself determine where slots are allocated.

So the legal substance lies in the procedural and evidential objections, while the commercial objections explain why the dispute is rancorous.

What the Law Says

Slots are regulated, not discretionary: At a coordinated airport, slot allocation is governed by the IATA Worldwide Slot Guidelines and, in India, by the Airports Slots Regulation 2021. Historical slots are protected. Reassignment or withdrawal follows a defined process administered by a slot coordinator, not by an airport operator’s email to airlines. MIAL’s communication to 46 carriers, setting a deadline of 2359 on October 25, does not appear to have followed that process.

OMDA is the constitutional document: Delhi and Mumbai airports operate under 30+30-year OMDAs, each of which sets out the operator’s development and capacity obligations and is the reference point for what the operator may do unilaterally. MIAL has not demonstrated in the public domain that the OMDA permits it to declare a capacity reduction and reassign slots on its own. The onus here lies with the operator, not the airlines.

Why the non-compete question does not arise: It is worth looking at an objection that would occur to anyone familiar with the sector: surely Mumbai airport’s OMDA protects it from a competing airport nearby? The answer: no, it does not. Unlike the Bengaluru and Hyderabad greenfield concessions, which carry a 150 km, 25-year exclusivity clause, Mumbai’s OMDA contains no such clause - the government had long known that a second airport for Mumbai would be needed, and Navi Mumbai was subsequently tendered without any legal challenge on record. Similarly, Navi Mumbai’s own framework grants it no exclusivity against Mumbai airport. So MIAL cannot claim territorial protection from Navi Mumbai’s existence.

But the absence of catchment protection is not a licence to permit the unilateral redistribution of traffic. These are two separate issues: territorial exclusivity (absent: no claim) and slot and capacity governance (regulated: and that is where MIAL is exposed). Conflating them would be erroneous.

The Real Issue

How is competitive discipline to be ensured when the state declines to impose it? The capacity constraint itself is not a figment of MIAL’s imagination - T1’s origins go back to the 1940s; Mumbai airport has operated for years on what is, effectively, a single busy runway. Nobody serious argues that the development should not happen. But this is precisely why the basis for the five-million figure matters: if the constraint is real and long-standing, MIAL should have no difficulty demonstrating the arithmetic. The fact that it has not is intriguing and, perhaps, the story.

And that story is symptomatic of something larger. Mumbai is the one major Indian airport where the state has deliberately avoided catchment protection. Having declined to protect CSMIA contractually, the state now finds both Mumbai and Navi Mumbai airports under the same corporate group — Adani Airport Holdings Limited. The coordination that the OMDA left to market forces is now happening inside a single operator. While this is not improper in itself, it changes the question: when the state declines to impose a non-compete, what replaces the competitive discipline it would have created?

The answer, on this record, is: a ministry acting as mediator rather than adjudicator, an operator deciding capacity and slot distribution on its own motion, and airlines objecting without a clear forum. This point is being made more bluntly on social media - that the same corporate group owning both airports in a megacity is a fit case for Competition Commission investigation. This is a sharper version of the question I have asked in this piece, and it deserves a straight answer rather than mediation.

Consider the choices embedded in the proposal: why cut international departures, i.e., higher-yield, longer-haul, more connectivity-sensitive traffic, rather than domestic? Domestic traffic would be the more natural candidate for an airport whose surface connectivity is still maturing, whereas the choice of international traffic suggests that the objective is to quickly establish Navi Mumbai as an international gateway. While this is a perfectly legitimate corporate strategy, it is not the same as a capacity-management necessity, and the two should not be presented as identical.

Also consider the framing: MIAL’s communication stresses that airlines have “complete freedom” to decide, that participation in consultations is “entirely at each airline’s individual discretion”, and that all historical slots will be restored once T1 reopens in 2030. This is the language of an operator building a record that any subsequent reduction was airline-driven rather than operator-imposed. That is legal-risk management, and should be read as such.

The Mumbai dispute is, incidentally, a short-horizon problem that is now appearing elsewhere over much longer horizons. Canada, for example, is currently considering 99-year concessions to operate its four largest airports. That’s a term long enough that the monitoring obligation outlives the institutions meant to discharge it, and long enough that the reversionary claim becomes legal fiction. Both cases turn on the same question: when the state steps away from building competitive or reversionary discipline into the concession, what corrects the operator’s decisions over time? In Mumbai, the answer is a ministry acting as mediator; in a 99-year concession, there is no answer at all.

The Gap That Needs to Be Closed

A word on the deadline, because it matters. The October 25 cutoff was proposed, not imposed. While MIAL has deferred the shift to Summer 2027 after the ministry’s intervention, this deferral does not obviate the proposal. The threat of a unilateral deadline was what triggered the dispute, and appears to be the template for how the operator intends to proceed once the T1 work begins. The deadline has been moved, but the logic behind it is unchanged.

The Ministry’s October 6 intervention asked MIAL to engage stakeholders on a mutually agreed transition plan. This is a “soft touch” intervention that has mediated the process without adjudicating the underlying question: does MIAL have the authority to do what has been proposed?

That question remains open, and the precedent it sets is larger than the dispute. If an operator can declare a capacity reduction, set a deadline and invite airlines to negotiate the distribution, with the regulator as facilitator rather than decision-maker, then the governance framework for Indian airports is less well-defined than the OMDA implies.

The ideal outcome is not for the ministry to pick a number, but for it, or the slot coordinator, to require MIAL to demonstrate the basis for the five-million number and the 265-departure reduction, and to confirm that the reassignment process complies with the Slot Regulation. If it does, the transition plan should be allowed to proceed. If it does not, the plan needs to be redesigned, not negotiated under deadlines.

Nobody disputes that T1 needs redevelopment. What remains unresolved is whether its cost is to be distributed by an operator’s decision or by a regulated process. It is an answerable question, but one that the ministry’s mediation has so far left untouched. An open question which is answerable, but the question the ministry’s mediation has so far left untouched.