The 60-year-old Terminal 1 (T1) is set for a major overhaul, targeted for completion by 2030, which will expand its annual capacity from 15 million to 20 million passengers. But construction means disruption. To make space for the work, Mumbai International Airport Ltd (MIAL) needs to restrict capacity equivalent to about 5 million passengers per year from the Summer 2027 schedule.
The immediate pressure falls on international operations. MIAL proposed cutting 265 of 770 weekly international departure slots (roughly 33%) at Terminal 2 to free up space for domestic passengers displaced from T1. This is where InterGlobe Aviation (IndiGo) and Air India Express face a tough choice: fight the cuts or move some flights to the new Navi Mumbai International Airport (NMIA). Both airlines, along with Adani Airport Holdings Ltd (AAHL), announced on October 25, 2026, that they would opt for a phased shift to NMIA.
IndiGo's strategy is clear: move the international flights that face the biggest slot cuts while keeping its massive domestic base at Mumbai. The airline faces the largest proposed reduction, with 74 of its 224 weekly international departures affected. By transferring 12 daily international departures to NMIA between February and July 2027, IndiGo directly relieves pressure on T2.
The destinations moving—Bahrain, Riyadh, Dammam, Jeddah, Madinah, Kuwait, Ras Al Khaimah, Fujairah, Muscat, Dhaka, Jakarta, and a new Kathmandu service—are mostly narrow-body routes suited to its A320neo and A321neo aircraft. Crucially, IndiGo is also shifting the domestic flights needed to feed these international services, allowing passengers to connect seamlessly at NMIA. This preserves its hub-style offering in the Mumbai region without abandoning its domestic stronghold at CSMIA.
For Air India Express, the move is about protecting its slot history at Mumbai while building a presence at NMIA. The airline will start with four daily domestic flights from NMIA in December 2026, followed by a phased shift of West Asia services from January 2027, including Oman and Kuwait (subject to approval). By the Northern Summer 2027 season, it plans to move services to Jeddah, Riyadh, Dammam, Doha, Muscat, and Sharjah.
Air India Group has emphasized that this phased shift preserves the "historicity" of its existing slots at CSMIA. Airport slot rules generally depend on historical use, and airlines that don't use slots risk losing them. A voluntary, documented relocation is a way to avoid being cut unilaterally while keeping the slots. MIAL has said historical slots, plus additional slots, will be restored once T1 reopens, though airlines are demanding compliance with slot guidelines before accepting any plan.
Both airlines are betting that short-term disruption pays off in long-term capacity. The transition is complex. It involves re-timing flights, coordinating terminal readiness at NMIA, and managing crew and aircraft rotations across two airports about 50 km apart. Passengers face longer ground travel and a higher User Development Fee at NMIA, though Adani Airports plans cash vouchers to offset the difference for international passengers.
However, the alternative—fighting slot cuts or suspending flights—carries its own risks. IndiGo's Q1 FY27 results show total cost per available seat kilometre (CASK) rose 32.6% year-on-year, partly due to lower utilization. A fragmented transition that leaves aircraft idle would add to that pressure. A well-planned transfer that keeps aircraft flying similar hours is the main lever to control costs. Adani Airports has also offered 100% landing-fee discounts on new international flights at NMIA, which could offset some duplicated expenses. Investor Presentation +1
IndiGo's fleet is well-suited for this shift. At June 30, 2026, it operated 432 aircraft, including 174 A320neos, 175 A321neos, and 3 A321XLRs. The airline has said international capacity will rise to about 40% by 2030, up from roughly 33% today, with XLR deliveries and incoming wide-bodies supporting this growth. The 12 daily departures moving to NMIA are primarily Gulf and nearby routes, ideal for its A320/A321 family. The longer-range A321XLRs, which IndiGo has begun flying from Mumbai on European routes, are likely to stay at CSMIA for now, though the company hasn't confirmed this. Investor Presentation +2
For Air India Express, operating from both airports expands its market coverage. NMIA's catchment includes Vashi, Belapur, Panvel, Thane, Kalyan, and Dombivli. The airline was the first to launch scheduled international flights from NMIA, starting with Abu Dhabi in July 2026. By shifting its West Asia services, it strengthens its position in a region where it already has a strong presence. However, higher fees and longer travel times for some passengers could dampen demand from south and central Mumbai, potentially benefiting rivals that stay at CSMIA.
The transition timeline depends on regulatory approvals and project coordination. Air India Express's Kuwait services are subject to required approvals. India and Kuwait signed a new air services agreement in July 2025, raising weekly seating capacity to 18,000 in each direction. With the route operating at full capacity, securing slots and entitlements for a new point of call at NMIA could be a constraint.
Final transition dates will be set after "project coordination is completed and relevant operating approvals are secured". This involves terminal readiness, slot timing, domestic feeder flights, and ground-handling logistics. Both airlines and AAHL have emphasized a "transparent and proportionate redistribution of capacity" based on each airline's presence at Mumbai airport.
Slot regulation adds another layer of uncertainty. Airlines have cited the Ministry of Civil Aviation's 2013 slot-allocation guidelines and International Air Transport Association rules, arguing that traffic reallocation cannot be done unilaterally. The Ministry intervened in October, asking MIAL to work with stakeholders on a mutually agreed plan rather than proceeding with its original proposal. An October 28 stakeholder meeting is expected to determine whether the sides can narrow their differences before the Summer 2027 schedule is finalized.
The two-airport system creates both advantages and risks. IndiGo and Air India Express gain first-mover advantages at NMIA, with early presence helping secure slot timing, gates, and brand awareness. They also benefit from landing-fee discounts and a negotiated transition, while other airlines, including foreign carriers like Air France-KLM, have resisted a shift.
However, the burden is not evenly shared. IndiGo faces the largest proposed cut, and if rivals stay at CSMIA while these two move, they may hold the more convenient airport for premium and time-sensitive passengers. Market share effects are hard to quantify without route-level data, but capacity is being moved, not cut, so seat share on these routes should remain stable across the two airports combined. In the short term, share at Mumbai airport alone would fall for these airlines, while share at NMIA would rise.
For passengers, the two-airport system offers more choice but also more complexity. NMIA is better located for some parts of the Mumbai region, but cross-airport connections are impractical. Passengers must carefully check their itineraries for the correct departure airport.
The phased transfer is a strategic bet on Mumbai's long-term aviation growth. Adani Enterprises expects the regulatory asset base for its airports to rise from about INR 37,000 crore to nearly INR 70,000 crore, driven by the Mumbai and Navi Mumbai additions. NMIA is scaling up rapidly, from 0.6 million passengers in Q4 FY26 to 1.7 million in Q1 FY27. Transcript +2
The success of this transition hinges on execution. If coordination is smooth and approvals come through, IndiGo and Air India Express could emerge stronger with a dual-airport presence. If disputes over slots and capacity drag on, the disruption could outweigh the benefits. All eyes are on the October 28 meeting and the final transition dates yet to be announced.
