layers, anything comfortable, especially if flying economy, by the time you arrive you are going to look like all the rest of your fellow passengers, creased wrinkled and worn out. no one will take any notice of you at an Indian airport, unless its a business trip.Suggest posh designer track bottoms.Are you changing planes in Mumbai or Delhi ?
If you wear jeans, shorts or a tee shirt they call you "hippies" behind your back and thats general widespread, we turned up for a dental appt and the receptionist smiled and was ever so polite and nice and then said down the phone in Urdu the two hippies are here, ufortunately for her my husband understands Urdu and she was made to apologise. Asked my sister in law [ I am cockney,husband is Goan] and she said yes we do call you all that and apparently its a no no to wear a tee shirt [ polo shirt acceptable] to meet a bank manager or similar status.
Plus side is laundry in hotels is ever so cheap and same day service.