Reducing passenger loading and unloading times (also called "Turn Times" in the industry) is a surprisingly hard problem that has been and continues to be heavily studied.

Field studies watching actual passengers loading actual planes (as opposed to computer simulations of theoretical "people" loading theoretical planes) frequently show the fastest loading when passengers are lined up randomly, ahead of any of the more seemingly "intelligent" approaches that work great in computer simulations. If the "best practice" algorithms can't even beat the random algorithm in a field study, that's a sign this is a much harder and much messier problem than it appears to be.

Just about any google search, like "airplane passenger loading research", will return more than a dozen theoretical and field studies on the first page of hits, including:

[0]The Role of Computer Simulation in Reducing Airplane Turn Time, https://www.boeing.com/commercial/aeromagazine/aero_01/texto...

[1]A Simulation Study Regarding Different Aircraft Boarding Strategies, https://upcommons.upc.edu/bitstream/handle/2117/19651/145014...

[2]Analysis of Airplane Boarding Times, https://www.researchgate.net/publication/220244330_Analysis_...

[3]Efficient Aircraft Boarding Strategies, https://labs.engineering.asu.edu/ilpil/research/efficient-ai...

[4]Passengers boarding airplanes: we’re doing it wrong, https://theconversation.com/passengers-boarding-airplanes-we...

[5]The Best Way to Board a Plane, https://phys.org/news/2008-02-board-plane.html

[6]Loading an Airliner Is Rocket Science, https://www.nytimes.com/2006/11/14/business/loading-an-airli...

[7]Comparative Study of Aircraft Boarding Strategies Using Cellular Discrete Event Simulation, https://www.mdpi.com/2226-4310/4/4/57

[8]Intelligent Boarding Modelling and Evaluation: A Simulation-Based Approach, https://www.hindawi.com/journals/jat/2021/9973336/

[9]Improving airplane boarding boarding time: a review, a field study and an experiment with a new way of hand luggage stowing, https://commons.erau.edu/cgi/viewcontent.cgi?article=1200&co...

[10]A Comparison of Algorithms That Estimate the Effectiveness of Commercial Airline Boarding Strategies, https://commons.erau.edu/cgi/viewcontent.cgi?article=1072&co...

[11]The Mathematics of Aircraft Boardingg, https://www.maa.org/external_archive/devlin/devlin_05_06.htm...

(among many others)