BELLBOTTOM is an espionage thriller, inspired by a true event. On August 24, 1984, ICC 691 flight takes off from Delhi and gets hijacked. This is the 5th hijack in 7 years. In the past, the hijackers landed their plane in Lahore, Pakistan, after which the Pakistani authorities negotiated and managed to get a safe release for the passengers.
This time, too, the flight moves to Lahore. Prime Minister of India, Indira Gandhi (Lara Dutta) is all set to negotiate. But she is stopped by a RAW agent, Anshul Malhotra aka Bell Bottom (Akshay Kumar). He has done extensive research on the past hijack operations. He is confident that ISI is the mastermind of the hijack episode. Indira Gandhi and her core team at first doesn't believe him. But he proves it to them the truth. Indira Gandhi then gets a call from the President of Pakistan, Zia-ul-Haq, to ask Indira if he can go ahead with the negotiations.
On the advise of Bell Bottom, Indira tells Zia-ul-Haq not to negotiate. The Pakistan President is taken aback by this conduct. The ISI then sends one of their best men, Daljeet Singh aka Doddy (Zain Khan Durrani) to take over the hijack operation from Lahore. For Bell Bottom, Doddy is someone he personally detests and with whom he has a past. What happens next, forms the rest of the film.