Originally Posted by
avidflyer
NW SWU's work at any fare. If you do not have those then you need to buy a B fare and use miles.
For US-India, this would be:
B Fare + 40,000 miles (each way)
Y Fare + 30,000 miles (each way)
Or trade for NWA SWU...good luck on that one though. Not only are these very prized, but they are rare.
More info on mileage upgrades from the USA can be found
here.