The duration of direct flights from Hanoi's Noi Bai International Airport to Sapa is approximately four to five hours, depending on the airline or flight schedule option chosen. You will leave Hanoi at about 6:00 AM local time and arrive in Sapa about 9:30 AM. Afterward, take an approximate two-three hour break for check-in at the hotels, either to squeeze in some sightseeing around Sapa, or to have a relaxed lunch.
The remaining aspect of travel involves the train. Just leave at the Long Bien Station or the Hanoi Station and arrive at Lao Cai Station, the closest stop to Sapa, in 8-9 hours. Here, a data shuttle or taxi will take you away for the last 40 minutes' journey toward Sapa town.
The overnight bus from Hanoi to Sapa usually takes about 6-7 hours, although these can take anywhere between 1 to 9 hours, depending on the kind of stopping and road conditions.
To get to Sapa, you can take bus or train. If by train, you should buy an overnight sleeper train from Hanoi to Lao Cai and then connect to Sapa by bus or higher level bus. If by bus, you can buy a direct bus (mostly sleeper-bus) from Hanoi to Sapa which costs you 5-6 hours depending on the day and the road. You can also take a private car, or taxi which can take you 4-5 hour but highly depends on the traffic and the weather.