The US, he discovered, operated 40,000 commercial flights a day, compared to 420 in India. He did a quick back-of-the envelope calculation: if 5% of the roughly 30 million Indians who travelled by train and bus began flying, that would translate into an eye-popping 530 million air travellers a year. “Even if this number looked huge, it did not mean 530 million different people travelling but 200 million middle-class people travelling two and half times a year, which was not an unimaginable prospect over the next 30 years,” he explains.
source: bbc.com