So then, plot does not matter.
It does, of course, but it gets to it in a different way. The primary focus of flash fiction is to present mental associations through words to the reader that will allow the reader to enter into whatever memory or knowledge they have which mirrors the associations of the character in the story at that moment in the piece of flash fiction.
In the example, it is a man going through an airport but if for a reader it is something else that is fine as long as it triggers the same associations of memory that were activated in the character’s mind while moving through the airport. Therefore, using the structure of flash fiction, a piece of writing does not need to create the same story for of all readers but rather only aims to express the feeling of the character(s) by using the words he/she associates with the experience being presented. This allows the reader to quite literally enter into the mind of the character because instead of the story telling the reader what the character is thinking or feeling, flash fiction allows the writer to show the reader how and what the brain of the character is connecting to create this moment in the narrative.