The main runway will remain shut for eight hours every day, except Sunday, till February next year as the airport operator Mumbai International Airport Limited (MIAL) is carrying out maintenance work.
"Some 15-20 flights were affected due to the main runway closure between 9 am-5 pm today. As the secondary runway does not have that much capacity, these flights were delayed by upto 30 minutes," an official with a domestic carrier said.
MIAL spokesperson was not available for comments.
The city airport handles close to 710 arrivals and departures including 520 domestic ones in 24 hours.
The cross-runway flight operations of the country's second busiest airport was in place since 2009 to maximise operational efficiency.
But since this April, the facility was scrapped after airport officials argued simultaneous use of both the runways was reducing the airport's capacity.
The idea behind cross-runway operation was to optimise the flight handling capacity to 45-48 aircraft per hour.
According to sources, in April this year, the Air Traffic Control (ATC) and the airport demanded that the cross-runway operations be scrapped as the capacity utilisation was still at around 40 flights per hour and that using the main runway alone increased this to 46 an hour.
With nearly a third of it surroundings covered with slums, the airport is starved of land. Last year too, there was a similar runway shutdown from November 30 to February 7.