Why Do Planes Stop Check-in 40 Minutes Before Departure?
Airlines typically advise passengers to arrive at the airport 2-3 hours before their flight. Once check-in closes, even if you arrive at the airport with enough time to reach the gate, you won't be allowed to board. This isn't due to inflexibility, but because of crucial pre-flight preparations that require a finalized passenger and baggage count.
Southern Airlines’ boarding prompt information, screenshot from the Southern Airlines official website
This isn’t because the airport or airline is being unreasonable, but because there’s a lot of preparation to do before a plane takes off, and some steps must be completed with the number of passengers and baggage confirmed.
The Important “Manifest”
Although the pilots and flight attendants have different pre-flight preparation tasks, they both focus on one important thing – the manifest.
Pilots need to enter the data on the manifest into the aircraft’s computer, and they must have the manifest before requesting takeoff from the tower, and then queuing up for takeoff according to instructions.
A key step in creating the manifest involves the airline or airport’s load control department calculating the aircraft’s weight and balance based on the aircraft type, range, fuel consumption, number of passengers (weight), and baggage weight, ensuring the aircraft’s center of gravity remains within a safe range.
Therefore, this step must be carried out when the number and weight of passengers and baggage are completely confirmed. If more passengers board, the passenger and baggage weight will change, and the aircraft’s weight and balance will need to be recalculated.
Therefore, flights are not allowed to check in 30 minutes (or even longer) before takeoff, otherwise it will delay the journey of other passengers.
The Importance of Weight and Balance and Center of Gravity
Although passengers don’t feel the “weight and balance” and “center of gravity” when flying, they are very important for flight safety.
For example, the crash of China Northern Airlines Flight 6136 in 2002 (also known as the 5.7 crash) was related to a change in the aircraft’s center of gravity.
The cause of this crash was arson. After the aircraft’s cabin caught fire, it was still able to fly for a distance. In this emergency, the pilot decided to avoid densely populated urban areas and ditch into the sea to minimize casualties on the ground. However, after the cabin caught fire, passengers instinctively rushed to the front of the cabin where the fire hadn’t spread, causing the aircraft’s center of gravity to shift suddenly forward, and the aircraft crashed headfirst into the sea.
In addition, in 2013, National Airlines Flight 102 crashed because cargo in the cargo hold was not secured properly and shifted during flight, causing the aircraft’s center of gravity to shift backward, resulting in a tragic accident.
According to a 2016 study, 77% of flight accidents were related to the aircraft’s center of gravity exceeding the safe range, and 57% of these accidents were fatal.
Given the importance of weight and balance and center of gravity to flight safety, it is necessary to give staff enough time to calculate, and to reasonably arrange baggage, fuel, and ballast.
By the way, when purchasing tickets, if the plane is not full, the airline will not allow passengers to choose seats freely, to avoid all passengers choosing one side of the plane, or concentrating in the front or back of the plane.
And during flight, even if seats in the front are empty, the crew usually won’t allow passengers to change seats at will.
For example, in 2015, there was a case where a passenger refused to sit in their assigned seat and insisted on moving to a front seat, causing other passengers to follow suit, ultimately affecting the aircraft’s weight and balance.
If Passengers Don’t Weigh Themselves, How Do They Know the Weight?
Since weight and balance are so important, how do the crew know our and our luggage’s weight? After all, only checked baggage is weighed during check-in, and people and carry-on luggage are not weighed.
The answer is simple: it’s estimated. Weight and balance and center of gravity are important, but they don’t require absolute precision.
According to the classification in the “Aircraft Weight and Balance Control Regulations” of the Civil Aviation Administration of China, most of the flights we take are “large cabin aircraft.”
For this type of aircraft, the “standard average weight” of passengers and baggage can be used for estimation. Because the larger the aircraft, the more passengers, the more accurate the estimation using the standard average weight.
Table of aircraft type classification in the “Aircraft Weight and Balance Control Regulations”
For example, the standard average weight of an adult is 75 kilograms, which includes the weight of clothing and carry-on luggage. The average weight of a child is 38 kilograms, and an infant is 10 kilograms.
Regulations on standard average passenger weight in the “Aircraft Weight and Balance Control Regulations”
Of course, the “standard average passenger weight” used in mainland China may not be applicable in other countries and regions. For example, according to data from the US Centers for Disease Control and Prevention (CDC), the average weight of American adult men is 90.63 kg (199.8 lbs), and women is 77.47 kg (170.8 lbs), plus the weight of clothing and luggage, which far exceeds 75 kg.
In addition, some airlines have restrictions on the size and weight of carry-on luggage, partly to ensure that luggage can be placed in the overhead compartments. It is also to prevent passengers from carrying too much carry-on luggage, which will affect the weight estimation.
Last-Minute Limit
Although planes stop check-in 30 minutes to 1 hour before takeoff, there may be special circumstances.
For example, some passengers who have completed check-in may be engrossed in shopping at the airport’s duty-free shops and haven’t arrived at the gate before the aircraft doors close.
When the gate is about to close, the airport will announce these passengers’ names as a reminder. But if they still don’t arrive after the announcement, the captain has the right to order a direct takeoff, as it’s impossible to let all the passengers on the plane wait.
In this case, the plane doesn’t necessarily need to recalculate the weight and balance.
There is a term called “last-minute correction,” which refers to the fact that before takeoff, after the manifest is completed, the flight can adjust the weight without re-creating the manifest. This includes adjustments to fuel weight, crew, passenger numbers, and cargo, etc.
This adjustment only needs to be filled in the remarks column of the manifest, and confirmed and signed by the captain and the personnel responsible for weight and balance.
For example, the following diagram shows the “last-minute correction” table on the manifest of a certain airline. The values that can be adjusted in the last-minute correction are related to the maximum zero-fuel weight, maximum takeoff weight, and maximum landing weight.
“Last-minute correction” part in the manifest of a certain airline
This manifest is for the A320-200 model, and can adjust up to 6 passengers or 500 kg of cargo. If the number of people or cargo changes too much, the weight and balance still needs to be recalculated and the manifest needs to be re-created. This will undoubtedly delay the time of other passengers on the flight, so after check-in, don’t forget to board on time.
In addition, when communicating with the pilots, there is also a detail worth noting. If all personnel are present, the cargo is loaded, and the aircraft doors are closed, and there are no restrictions on the route, you can apply for early takeoff. Although there are many prerequisites, you might be able to catch one!
Finally, I would like to remind you again that it is best to arrive at the airport early when traveling by plane, and pay attention to the boarding time after check-in. This will not only ensure a smooth journey, but also show respect for other passengers and crew members.