NRI’s are entitled to obtain aadhar number on their arrival in India.
NRI’s with Indian passport can apply for biometric ID on arrival or schedule an prior appointment.
Valid Indian passport will be accepted as a proof of identity, proof of address and date of birth document for NRI.
If an NRI passport doesn’t have Indian address then NRI is allowed to submit UIDAI approved POA document as a proof of address.
The above information has been obtained from the circular issued by UIDAI.