The lowest one-way fare for Delhi-Mumbai is Rs 1,599, while Delhi-Ahmedabad fare is Rs 999. The flight operates three times a week.
After two more aircraft join its fleet next month, the airline plans to launch more late-night flights on Delhi-Bangalore, Delhi-Pune or Delhi-Goa sectors, SpiceJet's promoter, Ajay Singh, said in a statement.
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The airline chairman, Siddhant Sharma, said the 98 per cent load factor in the last two days was totally unexpected.
"When the flight took off at 0330 hours from Ahmedabad, there were 32 passengers still at the airport who could not get a seat," he added.
Singh said the high demand for night flights would also benefit the airport authorities as it would spread the passenger loads at airports during day-time.