Air traffic control in the city faced an intense situation on the intervening night of Tuesday and Wednesday, scrambling to divert numerous international flights as Pakistan abruptly closed its air corridors beginning 10 minutes past midnight.
While air traffic controllers and pilots managing the diverted flights were unaware that Operation Sindoor was underway, they recognised something significant was happening due to the unusual closure of multiple air routes.
According to Calcutta airport sources, Pakistani authorities began shutting down air routes at 12.10am on Wednesday (Indian Standard Time). By 1.30am IST, Pakistan’s entire airspace was closed. The closure lasted until 4.15am.
In response, India closed 25 international flight routes that passed through Indian territory into Pakistani airspace, beginning at 4.31pm on Wednesday. As of late Wednesday evening, this closure was scheduled to continue until 5.30am on May 10.
Between 12.10am and 1.30am on Wednesday, Pakistan issued eight NOTAMs (Notice to Air Men) affecting routes from India. NOTAMs alert pilots and flight operations personnel about temporary closures that could affect flights, whether due to weather conditions or situations such as military conflicts.
“We’ve never experienced such a chaotic night at air traffic control. It seemed Pakistan’s civil aviation authorities were frantically closing one air route after another,” recalled a Calcutta airport official. “We understood something significant was happening, but didn’t know what.”
The first indication of disruption came shortly before midnight on Tuesday, when Lahore’s air traffic control contacted Delhi’s ATC through a hotline, verbally informing them of impending closures of Pakistani air routes used by international flights from India. Delhi’s ATC then relayed this information to Calcutta.
The first formal communication about closing three air route points in Pakistan arrived at 12.10am on Wednesday. Among these was Merun, an air route point within Pakistani airspace that serves as a boundary in the Delhi flight information region.
Pakistan continued closing additional routes until approximately 1.30am, when Pakistani aviation authorities formally notified ATCs globally that the country’s airspace was closed.
The abrupt closures forced Calcutta’s air traffic controllers to rapidly divert a substantial number of flights. Numerous international flights from Southeast Asia, the Far East, Australia, and New Zealand typically flyover Calcutta’s flight information region en route to Europe.
“Normally, these flights pass over Rajshahi in Bangladesh, then continue over Patna, Lucknow, and Delhi before entering Pakistan,” explained an airport official. Early Wednesday, flights had to be diverted through Jabalpur, Bhopal, and Mumbai instead.
“The closures happened so suddenly that some flights had already reached Patna or Lucknow, requiring last-minute diversions,” the official noted. According to him, more than 150 overflying flights needed to be rerouted.
The closure of 25 air routes within India means international flights will continue operating on diverted, longer routes. “Within Calcutta’s flight information region alone, this adds 30 to 45 minutes to flight times,” an official said.
Several airlines have announced flight cancellations. Calcutta airport sources reported that three IndiGo flights from Calcutta to Chandigarh, Srinagar, and Amritsar were cancelled on Wednesday.
“Due to government notification on airspace restrictions, over 165 IndiGo flights from multiple airports (Amritsar, Bikaner, Chandigarh, Dharamsala, Gwalior, Jammu, Jodhpur, Kishangarh, Leh, Rajkot, and Srinagar) are cancelled until 5.29am on May 10, 2025,” stated an IndiGo spokesperson.
“Passengers should check their flight status on our website or mobile app before heading to the airport. Those affected can reschedule on the next available flight or cancel their bookings at no additional cost, with a full refund to be processed,” the spokesperson added.