At least 100 domestic flights a day to and from the Delhi airport have been cancelled during the nine days leading up to Republic Day, the Hindustan Times reported on Saturday.

Some air traffic is disrupted for about a week every year before Republic Day, but flights in the past have been rescheduled, not cancelled. This year, however, rescheduling them is not possible because of congestion at the airport, the newspaper quoted unidentified officials as saying.

The airspace over Delhi is closed for 60 minutes to 90 minutes daily for a week ahead of January 26 for rehearsals of the Republic Day parade every year.

This year, the airspace will be closed for passenger traffic from January 18 to January 26 between 10.35 am and 12.15 pm, a notice from the Airport Authority of India to airlines on Thursday said. International flights during these time slots will be rescheduled.

About 15,000 passengers are likely to be affected every day because of the decision.

“Rescheduling flights is not an option anymore because we have no extra slots,” an unidentified airport official was quoted as saying. “If we try to adjust, it will disrupt the entire day’s schedule. So we have decided to cancel the domestic flights that were meant to operate during the shutdown period.”

The Delhi International Airport Limited has called a meeting with the airlines on Monday to discuss the subject, The Economic Times reported.