Taxis between Noi Bai airport and Hanoi should still be $10. There are rows of taxis waiting ouside the airport. As soon as you exit, someone will take you to one. Make sure you confirm it's $10. Also, my taxi driver tried to get me to agree to $12 after I got in despite the agreement with the dispatcher. Insist on the $10 rate. Don't spoil things for others.
On the way back to the airport, there's a big taxi stand on Quang Trung not far from Lake Hoan Kiem (opposite Vietnam Airlines office) that has a sign for a $10 trip to the airport. You can make an arrangement here for them to pick you up at your hotel. They'll try to get you to agree to a higher price. Just point to the sign and insist on $10.
There're places in the old town that advertised $7 to the airport too.
Only use Hanoi Taxi. Used another taxi service (small green taxis) once to return to our hotel after eating dinner at a restaurant and the fare was 40% higher (28000 versus 20000 to get there by Hanoi Taxi).
I have lived in Hanoi several months now.... there are many taxi companies and one of the first things you will share with is what taxi companies you can trust. Mai Linh with its green and white large cars is touted by all hotels in Hanoi to be reputable. Compared to other reputable companies (thanh nga, thang cong) it is expensive so we never ever take it, but tonight there were no other options so we opted for the costly cab. We live less than a half kilometer from the bar we were at but it is across the highway so we thought what the hell let's splurge. The cost according to the meter was 28,000 dong and I gave the driver 30,000 dong. He saw the amount and immediately said no the cost was 80,000 because it was 2am...do NOT let a driver fool you into thinking taxis cost more late at night, they do not! I replied that was not true and I was even tipping him a bit and his reply was 'F*** YOU'... as a girl, this scared me and I threw the money in the front seat and ran to my apartment building. The driver got out of the taxi and followed my roommate and I across the street screaming 'F*** YOU' until he saw we were entering an apartment building with a security guard. In all my time in Hanoi I have never felt so scared and intimidated by anyone. I would never take this company again.
Noibai Taxi very Safe and Helpful, driver was very co operative he helped in my luggage . Would recommend to others to use this taxi service.
When you arrive at Noi Bai Airport, a convenient way to get to Hanoi town is to hire a taxi - it's USD10/- per taxi. Maximum passengers is 4 adults.
If you are quoted a higher price, bargain for it.