Join Date: May 2004
Location: SIN (LEJ once a year)
Programs: SQ, LH, BA, IHG Diamond AMB, HH Gold, SLH Indulged, Accor Gold, Hyatt Discoverist
Posts: 7,739
Altea has a mechanism that will flag out duplicate bookings so it is entirely possible for them to detect two different bookings for the same person on same flight, date, cabin, etc.
Now if such booking was made using a KF profile or such, they can tell for sure whether it is the same person. If it is two TA/OTA type booking with only first and last name it is a bit harder to tell whether two Michael Smith are the same person or different ones.
I have had this situation before, usually when booking corporate travel where say we confirm SIN-CGK in Y fare bucket and our corporate TA waitlists an E fare for the exact same itinerary as it will save 200-300S$. When the waitlist gets confirmed we are then given x hours / y days to pick one confirmed set of flights and cancel the other. Else SQ will cancel one automatically. YMMV