Ratan Tata is an honest business man ,in this sentence why we use an while an use with the vowel.

an is used for vowel as well words which sounds like vowel. here though it starts with "H" but it sounds "O". so it seems vowel and u will hv to use an

we use an for honest. because pronunciation of honest starts with O. that's why we use an not a. same ex. an hour.