What's the most efficient way to board a plane? Rear to front, randomly or by adapting scientifically calculated methods?
Over the years airlines have experimented with ways to get passengers seated as quickly as possible, but only with recent technology have some real alternatives been made possible.
Research by Boeing showed that the pace at which passengers board a plane has slowed by 50% since 1970. Reasons might include a longer list of priority boarders and more carry-on baggage blocking the aisles.
Quicker boarding time means airlines save money; $30 for every minute saved, according to studies.
"Planes make money in the air, not on the ground," Jan van Helden, project leader for KLM's "Smarter Boarding" program told CNN.
So, is there an ultimate boarding method? Not yet, but here are some of the efforts that have been made by airports, airlines and even one astrophysicist.
Passengers traveling with South African Airways from Heathrow airport took part of a two month self-boarding trial earlier this year that used biometric data.
Before boarding, passengers went through an electronic barrier that scanned their faces. The scan was then compared to an earlier face scan carried out during check-in or security. If the biometric data matched, the passenger could board.
"The specific application of this trial is to remove the need for a passport check," Mark Walker, passenger process program manager at Heathrow, told CNN.
He said the trial resulted in good transaction time for the airline.
"In the future there is a real opportunity for airlines to say that rather than having their staff checking passports and boarding passes, they can instead use the time to add real value to the journey of the passenger."
The 'positive' approach
Another new boarding technique being tried at London's busiest airport is called "Positive Boarding." It has been put to the test by Virgin Atlantic and United Airlines.
Passenger data is collected when boarding passes are scanned at security. The system then sends this data to the airlines, which then verifies if the passenger is in the correct terminal and how much time they have to reach their gate.
Messages are also sent to the passenger to inform them of the flight status.
"This allows the airlines to more quickly determine if a passenger is too late to board, so they can make a decision if they are going to offload a bag," explained Walker.
The cheese counter method
Dutch airline KLM claim to be the first carrier to come up with an innovative boarding technique they call "Smart Boarding."
"The breakthrough idea we had was to translate each passenger's seat number into a sequence number," said van Helden.
The numbers are then displayed on a big screen at the departure gate at five-second intervals, allowing only one person at a time to board the plane.
So far "Smart Boarding" has been used daily on three European flights departing from Amsterdam's Schiphol airport.
"It works very well for us and we board faster, 20% faster," van Helden said.
The astrophysicist's solution
When standing in line to board a plane, Jason Steffen, astrophysicist at Fermi National Laboratory in Illinois, wondered if there wasn't a better way to go about it. He tested different methods in computer simulations and came up with a method suggesting boarding in alternate rows, from rear to front, and window to aisle.
"The test we did, where we involved real people, showed that my method was twice as efficient as the common rear to front method," Steffen said.
"There was a recent show where they tested my method against that of Southwest Airlines, and mine was about 30% faster."