The advantage of checking in online lies in its speed and simplicity. What's even more special is that during the online check-in process, passengers can choose their seats on the plane.
Do you need to go to the counter if you've checked in for a flight online?
For cases with only carry-on baggage:
Passengers who have completed online check-in via the website, mobile app, or airport kiosks need to present the Boarding Pass at the Security Checkpoint and be at the gate before the time indicated on the Boarding Pass, especially for those with only carry-on baggage.
For cases with checked baggage:
Passengers who have completed online check-in via the website, mobile app, or airport kiosks need to visit the airline's counter to check their baggage and have their checked luggage screened before reaching the Security Checkpoint.
However, during certain specific periods such as peak times, holidays, Tet, or for some special reasons related to the regulations of airlines or the Civil Aviation Authority, passengers who have completed online check-in may still be required to visit the counter for verification of relevant information.

For VietnamAirlines
The online check-in process must meet the following conditions:
– The online check-in time is from 24 hours to 1 hour before the scheduled departure time of the flight.
– Each online check-in can only be done for a maximum of 9 passengers within the SAME booking code. If a booking code has more than 9 passengers, each passenger needs to perform online check-in multiple times for all passengers in the booking code.
– The online check-in service of VietnamAirlines is applicable only for flights operated and departing from the following airports:
Domestic
Cam Ranh International Airport – Nha Trang
Da Nang International Airport – Da Nang
Noi Bai International Airport – Hanoi
Tan Son Nhat International Airport – Ho Chi Minh City
Van Don International Airport – Quang Ninh
International
+ Southeast Asia
Bangkok – Suvarnabhumi International Airport (BKK)
Jakarta – Soekarno–Hatta International Airport (CGK)
Kuala Lumpur – Kuala Lumpur International Airport (KUL)
Luang Prabang – Luang Prabang International Airport (LPQ)
Phnom Penh – Phnom Penh International Airport (PNH)
Siem Reap – Siem Reap International Airport (REP)
Singapore – Changi International Airport (SIN)
Vientiane – Wattay International Airport (VTE)
Yangon – Yangon International Airport (RGN)
+ Northeast Asia
Beijing – Capital International Airport (PEK)
Busan – Gimhae International Airport (PUS)
Taiwan – Kaohsiung International Airport (KHH)
Taiwan – Taoyuan International Airport (TPE)
Fukuoka – Fukuoka International Airport (FUK)
Hong Kong – Hong Kong International Airport (HKG)
Nagoya – Chubu Centrair International Airport (NGO)
Osaka – Kansai International Airport (KIX)
Guangzhou – Guangzhou Baiyun International Airport (CAN)
Seoul – Incheon International Airport (ICN)
Chengdu – Chengdu Shuangliu International Airport (CTU)
Tokyo – Haneda International Airport (HND)
Tokyo – Narita International Airport (NRT)
Shanghai – Pudong International Airport (PVG)
+ Europe
Frankfurt – Frankfurt International Airport (FRA)
London – London Heathrow International Airport (LHR)
Moscow – Domodedovo International Airport (DME)

For VietjetAir
Currently, online check-in is applicable only for domestic flights departing from 3 airports: Tan Son Nhat, Noi Bai, and Da Nang. You can check in online within a period from 24 hours to 1 hour before the scheduled departure time. Note that online check-in does not apply if a booking code has more than 9 passengers.
For Bamboo Airways
– Online check-in is applicable only for Bamboo Airways' domestic flights departing from Noi Bai (HAN), Da Nang (DAD), Tan Son Nhat (SGN), and Nha Trang (CXR).
– Passengers can complete online check-in from 24 hours to 1 hour before departure and are required to submit mandatory electronic health declarations on flights as per the Ministry of Health's request, by visiting the website www.tokhaiyte.vn or downloading the 'Vietnam Health Declaration' app for iOS or Android devices.
– Online check-in DOES NOT apply to the following cases:
+ Passengers with special service requests (excluding special meal services).
+ Passengers refused carriage or deported.
+ Passengers traveling with infants under 2 years old or pregnant passengers.
+ More than 9 passengers under the same booking code.
As per Mytour
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Reference: Travel Guide from Mytour
MytourSeptember 29, 2020