As Air India's passenger service system (PSS) software shut down for six hours Saturday, the airline said a total of 155 flights will be delayed for an average duration of two hours till 8.30 pm.

Thousands of passengers had a harrowing time Saturday morning at airports across the world as the airline's PSS software, which looks after check-in, baggage and reservation, did not function from 3.30 am to 8.45 am due to a technical glitch.

"155 flights, with an average duration of two hours, are expected to be delayed till 2030 hours," Air India spokesperson said.

The airline's chairman and managing director (CMD) Ashwani Lohani said he expects normalisation of operations by Saturday night.

The average number of flights that Air India group, which also includes subsidiaries Alliance Air and Air India Express, flies daily are around 674.