Completely useless info but hey doesn't hurt to learn new stuff. This is on how VT came about as the registration/call sign of Indian civil aircraft.
Starting with the initials VT, the registration number of all Indian civil aircraft serves as a reminder of the country’s colonial past. Standing for Viceroy’s Territory, the registration prefix VT was assigned to India in 1929, and it continues ever since. So whether it is an Indian Airlines, Air-India, Jet or a Sahara owned aircraft, all have the prefix VT in their registration numbers.
And looks like good ol officials in Indian govt want to change it.
More info here: