INSIDE EDITION - The man appears to retaliate by shoving his hand into the attendant’s shoulder and face.
That's when the attendant lands a punch to the father's face, much to the shock of horrified bystanders.
A photo of the incident that catches the exact moment the punch was thrown. It was posted by English witness Arabella Arkwright.
Arkwright said the man did not deserve the treatment he received.
"The lies, lack of information and disinterest of easyJet's skeleton staff coupled with the inefficiency of easyJet in what should have been regarded as a customer service crisis and potential PR disaster has to be seen to be believed," Arkwright wrote in an open letter to the British airline.
Arkwright's letter continued:
"And then after 13.5 hours delay an official took a swipe at the father of one of these small children who was understandably remonstrating with him for the appalling treatment received; we have iPhone photos of both the swipe and crying children stuck in the boarding tunnel - but I don't suppose for a moment that these would be of any interest to you even tho' the father of the child was removed by the police who told him that he would not be traveling that night!"
Arkwright's letter makes a plea for easyJet CEO Carolyn McCall to personally and in writing apologize and offer an explanation to all passengers affected.
While it's unclear if that will happen, the company released the following statement Sunday, which stressed that the airport employee who threw the punch was not an easyJet employee..
"Passengers were provided with updates and refreshment vouchers during this time and the flight landed in London Luton [Airport] last night.
"The safety and well-being of our passengers and crew is always easyJet's highest priority. EasyJet sincerely apologizes for the delay and thanks passengers for their patience."