Americans service sucks! Here is what happened: we want to extend my parent's ticket from January to February. Original ticket was bought from China at $800 (CNY6000) for round trip and half year valid. We called trice NW Airline and they said the changing cost was "$1000 + $100 change fee = $1100". When we were arguing that this was a price gauging, they hung up on us!!
On the contrast, our Chinese travel agency was very helpful and very polite and trying their best to minimize our loss.
猜想这个坛子里的兄弟姐妹们(或父母们)一定也时不时地在中美间走动，千万不要乘西北了 (EVEN IF IT MIGHT BE CHEAPER - in our case, we have to buy another single trip ticket to China now, instead of paying $1000!. - MUCH MORE EXPENSIVE THAN IF WE JUST HAD BOUGHT TICKETS FROM OTHER AIRLINES。
If you search on Google, you'll find tons of tons of compaints about Northwest.
叹美国服务业之劣，中国服务业之进步！ MAY NORTHWEST AIRLINE FILE BANKRUPCY ASAP！