Best way to get to Vientiane from Hanoi

The best way to get to Vientiane from Hanoi is to fly. There's also a direct bus that's much cheaper than flying but takes significantly longer. So whether you should fly or bus depends on your budget and time
Flight from Hanoi to Vientiane:
This is how the vast majority of travelers, tourists or local, travel between these two cities
There are 4 daily direct flights on this route:
Vietnam Airlines - 9:35AM -> 10:50AM
Vietnam Airlines - 9:55AM -> 11:05AM
Lao Airlines - 4:20PM -> 5:30PM
Lao Airlines - 4:40PM -> 5:50PM
Fare is $120-$140 USD per person each way
Flight takes 1h15min

Bus from Hanoi to Vientiane:
The only direct bus on this route is operated by HTX Van Tai 277
This is a semi-sleeper bus (meaning you don't get a bed but large a seat with steep recline), which takes 24 hours to get to Vientiane
Fare is just $24USD per person, departing at 5pm and arriving at 5pm the following day
This bus gets a 2.4/5 star review, mostly because of the duration, unfriendliness of the staff, unclean toilet, and no wifi. It is air conditioned. This is what the bus looks like inside:
At the border crossing, you will be responsible for your own paperwork. You need to make sure that you have everything needed to get a visa to Laos
The bus departs from Hanoi Nuoc Ngam Bus Station, located here. It is quite a bit south of the historic city center, French Quarter, and West Lake area so you will need to taxi. The taxi fare is approximately 160,000 dongs ($7USD) from the French Quarter
The bus arrives in Vientiane Southern Bus Station, located here
The only way to book this bus is to use 12Go (https://12go.asia). Just put in Hanoi as your origin and Vientiane as your destination

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