New Delhi/Mumbai: National carrier Air India expects operations to normalise by Saturday night after its flights were delayed due to a software glitch which hindered essential services like check-in, baggage handling and boarding.

Accordingly, 155 flights of the airline group operated by Air India, Air India Express and Alliance Air were expected to be delayed till 8.30 p.m.

The trouble started after Air India's passenger system server operated by global airline IT major SITA, was affected with a glitch while undergoing scheduled maintenance early Saturday.

Briefing the media in New Delhi, Air India Chairman Ashwani Lohani said that 85 flights of Air India Group were delayed till 10 a.m. on Saturday.

According to Lohani, the ripple effect of the initial cancellations will continue throughout the day on the domestic network, while the international flights will mostly operate on time.

The airline operates 470 flights per day while the Air India Group provides 674 flight services.

Lohani said the system has been restored and passengers are being informed well in advance about the status of their flights.

He added that some flights have also been rescheduled.

Early Saturday morning, flight operations were hit for over five hours after the glitch was reported in the SITA server.

At Mumbai's Chhatrapati Shivaji Maharaj International Airport, ranked among the busiest airports in the world, thousands of passengers were stranded and many flights were affected since 3.30 a.m.

"Due to a breakdown in our server system some of our flights are getting affected all over the world. Work is on in full swing to restore the system," the airline said in a statement earlier.

In response, SITA said that it experienced a complex system issue during server maintenance, which resulted in the operational disruptions.

"We have now fully restored services at all airports where Air India was affected. Our priority remains, as always, to ensure a stable system where customers can conduct business efficiently and effectively, and we are undertaking a full investigation to understand the root cause and prevent a recurrence.

"We deeply regret the inconvenience this has caused to the airline and their esteemed customers owing to this disruption," it added. (IANS)

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