new delhi, Nov. 12 -- Gulf Air and Saudia are both opposing Adani Airport Holdings' proposal to reduce capacity at Mumbai and shift a significant portion of the international operations to Navi Mumbai. The proposal has sparked a fight that could well, in the end, involve the regulators, the diplomats and the various governments concerned. The Navi Mumbai airport is 50km from Mumbai airport. At the core of the dispute are the long-standing flight slots. Both airlines are adamant that Adani has no right to unilaterally scrap the historic slot allocations and warn that they may take their case to the civil aviation authorities in India, Bahrain and Saudi Arabia. Gulf Air has suggested the prospect of countermeasures, which would mean that Indian carriers could, in turn, be squeezed on slots abroad under the various bilateral air service agreements. Saudia has added further fuel to the fire over the timing of the proposed slot reductions, with a sudden cutback posing a real threat to the annual Hajj and the year-round Umrah pilgrimage traffic. Mumbai is one of India's key departure points for Muslims heading to Mecca, with some 26,000 pilgrims going overseas from there last year alone. Adani says the capacity reductions are simply a necessary operational headache to deal with the severe congestion in Mumbai and to route traffic to the new Navi Mumbai airport in the run-up to the major redevelopment of the terminals. With neither side willing to back down, the impasse could disrupt international flight schedules, put pressure on diplomatic aviation relations, and make the long-anticipated move to a dual-airport city far more fraught. MIAL is a joint venture between Adani Airport and Airports Authority of India (AAI). "MIAL cannot unilaterally reduce airport capacity, disregard established historical slot entitlements, or compel Gulf Air to surrender its existing operational positions based on a redevelopment plan," Gulf Air said in an email last week. "In the absence of a satisfactory reply, Gulf Air will escalate the matter formally to the Ministry of Civil Aviation, the DGCA, and the Bahrain Civil Aviation Affairs, and will raise it with IATA, including consideration of reciprocal measures under the applicable bilateral air services arrangements," the email further said. Gulf Air flies twice daily from Mumbai. Saudia also challenged the cut process, reasoning, and transparency. "More importantly, the decision has direct implications for Hajj and Umrah operations from India. As the national carrier of the Kingdom of Saudi Arabia," Saudia said in a separate email to Mumbai airport last week....