The Bharatiya Janata Party (BJP) sought permission for the helicopter to land at the Race Course ground near the Brigade Parade Ground, the rally venue. The army is the custodian of both grounds.
After being earlier denied permission for the helicopter landing, state BJP president Rahul Sinha accused the central government of "intentionally denying the permission in pursuance of a conspiracy".
Sinha later said the permission to land the chopper was granted.
"Due to a massive media outcry, the Congress was forced to concede ground. The permission was granted as a damage control measure," he said.
Led by Modi, the BJP will Wednesday kickstart its campaign in West Bengal for the general election.