Megastar Amitabh Bachchan has revealed that he was not allowed to board a flight to the US after the September 11 terrorist attacks in the country in 2001.

During that time, he stayed in a hotel room for three "treacherous" days.

"9/11 was most tragic and sad and frightening" I was shooting for 'Kaante' in Los Angeles and had taken a couple of days off to travel to Egypt for the International Film Festival in Alexandria, where they were honouring me with a special award," Amitabh recalled on his blog on Monday on the 16th anniversary of the terrorist attacks.

"Ceremony over, the next morning I took a flight out of Cairo, to Los Angeles via London.. Arrived in London, Heathrow Airport, and after a short wait was announced to board my flight to Los Angeles via New York City," he added.

The 74-year-old said when he was about to board the flight he got a call from "very frantic and screaming Shweta (Nanda) from Delhi" who asked him to see TV.

"I did not have time to ask why, and I think it was quite obvious that something important and serious was happening ... also immediately there was a sudden commotion in the entire airport ... people were moving about rather rapidly in all directions, some with muffled screams and a large portion of them running to the large TV screen at the terminal," Amitabh said.

He said he saw one plane hitting the World Trade Center on TV.

He added: "Motionless and in shock and stunned silence, people watched the second one go in too and it was a most inexplainable situation .. some had anger written all over them, some were in tears, others were frantically making calls ...

"I just stood there for a while stunned and then quietly walked across to my gate to board the flight ... boarded, taxied off and then the plane turned back ... announcement ... all flights to and from US blocked and stopped."

Amitabh said that he stayed in a hotel for next three days.

"Airline after much to and fro arranged for us to get to a hotel and there we stayed for the next three days until there was clearance to travel," Amitabh said.

"Those three days at the hotel were treacherous ... did not move from the room and only watched TV giving news of the incident and talks and debates and details of what and why and where and how. A sad moment.

"A few years later I on a visit to New York had driven past the site, where preparations were being done to rebuild the spot with a memorial," he added.