Come to think of it, if pax would provide their aadhar card number in the reservation as form of ID (FOID) you could pick up the biometric data from there. The BoI system already has the biometric info of all foreigners captured from their passports and validated/crosschecked at the port of entry, so they could use that too. Just like the US CBP already provides the data for biometric boarding on international flights (eg SFO) and the TSA just scans your ID/passport and knows you have a flight that day from that airport.