It has happened on more than one occasion to me - travelling next to celebrities. I have left them absolutely alone after wishing them a polite hello which also indicated that I knew who they were. At the end of the journey, each of them has thanked me for leaving them to recollect their thoughts and bearings.
The first one was Rajiv Gandhi who was travelling from Bombay to Delhi as a passenger in 1976. Second was Mallika Sarabhai in around 1982, Bangalore - Delhi and apart from 4 others, the last one was Ramanathan Krishnan.
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This reminded me of my interesting Air Travel 25 years back, I was travelling from Chennai to Bangalore in the morning flight , I was not a frequent Air traveler, I was instructed to put on my seat belt , Mr. Jemini Ganesan was siting next to me , I noticed him , I was trying with the seat belts ,but i got two female hooks together to fasten, Mr. Gemini was also trying to fasten the seat belt ,He was left with two male hooks ,and searching for the female pair , which I was holding and helplessly and trying to fasten ,on noticing me ,he reached out for the female hook from my hands with a a smile and amusement and helped me fasten my seat belt in tact.,he gave me a candy also with a pat . I thanked him with a thrill . This experience still linkers in my mind and make me well amused always even now.