Mumbai, Aug. 27 -- The loss-making Mumbai Metropolitan Region Development Authority (MMRDA) is staring at a potential hit of Rs.250 crore owing to a design and construction flaw on the Metro 7A corridor, officials familiar with the matter told Hindustan Times. The planning authority had, in early 2025, sought relaxation of height restrictions for the Airport Colony metro station, viaducts and ramp area, after it was found that the under-construction structure was breaching the air funnel or path followed by aircraft operating from the Chhatrapati Shivaji Maharaj International Airport (CSMIA). Though the Airport Authority of India (AAI) is yet to revert to MMRDA's application, officials fear they may have to demolish and reconstruct a large chunk of the Airport Colony metro station for violation of safety norms. The 3.42-km Metro 7A line links Terminal 2 at the CSMIA with Mira-Bhayandar and south Mumbai via the underground Metro 3 or Aqua line. In November 2023, the MMRDA had sought clearance from the AAI to construct the Airport Colony station and ramp area. On January 2, 2024, the AAI gave clearance, but the height was 2.9 metres lower than the project's design requirement. "This restriction immediately caused delays as construction could not proceed in this section without complying with the height limitation. MMRDA was forced to halt work in the affected areas, which began to disrupt the overall project timeline," said an internal document accessed by HT. On January 31, 2024, the MMRDA sought another clearance for the viaduct between the Airport Colony station and the ramp. This time too, the AAI issued a No Objection Certificate (NOC) on March 18, 2024, limiting the viaduct's height to 0.53-2.75 metres, which was lower than the height required for safe operation of the metro system. Hence, work came to a standstill once again, and it also came to light that the Airport Colony station had been "designed without referring to the contents of the NOC and the drawings were also issued with a higher height," according to the MMRDA internal document. Subsequently, the MMRDA approached the AAI again seeking height relaxation for the entire structure, reasoning that altering the metro line's height was impossible due to engineering challenges in maintaining the ramp's gradient, the official quoted earlier said. If the AAI rejects the MMRDA's plea, the project cost, currently at Rs.812 crore, will increase by approximately Rs.250 crore, as a portion of the Airport Colony metro station and installed systems will have to be demolished, officials said. Consequently, the MMRDA is likely to miss the target of having a Rs.17-lakh surplus budget for the ongoing fiscal (2026-27). During the 2025-26 financial year, MMRDA's losses as per revised estimates stood at Rs.997 crore....