The most important factor is timezone.

When compared to Eastern Time, Singapore is 12–13 hours ahead. Making a call to a Singaporean line during regular US business hours usually entails dealing with foreign workers that work late into the night or sitting through lengthy wait times.
A local point of contact is preferred by New York passengers. Calling the Singapore Airlines Phone Number New York puts customers in touch with representatives that are familiar with U.S. departure processes, the ins and outs of JFK Airport, and the travel habits of American consumers.