Aviation sources said Bareilly airport was under the Indian Air Force and hence all civilian aircraft required air defence clearances, which his aircraft did not have.
They also said the private charter company, which was based in Ahmedabad, was filing flight plans just minutes before actual take off time, which was causing the delays.
Due to this, air traffic control was not clearing the flights as no instruction reached them in time for the aircraft to take off on schedule, the sources said.
Addressing a rally in Bareilly, Modi told the gathering, "I apologise to you for arriving late as you had to sit in this heat. But this delay was not because of me. At the Delhi airport I sat 9.30 AM onwards but our helicopter was not being given the permission to fly."