Vive La Reine sets the record straight on some common misconceptions about the royal family's flight to Varennes. To quote:
Louis XVI intended to flee France
Louis XVI firmly refused to leave the country and, according to biographers such as Fraser, Webster, Hardman and more, turned down several flight routes to Montmedy which would have been much faster and safer because they briefly took him across the French border.
The coach which carried the royal family was recognized because it bore their royal arms/was too extravagant
The coach, presumably ordered by Axel Fersen, was large but not unusually so and was in fact based upon previously drafted plans for a Parisian’ companies carriage. It was not decorated with the arms of the royal family and, on the outside, was nothing out of the ordinary. The coach featured a variety of traveling amenities often used by those who could afford them - including a larder, cooker, fold-up table and chamber pots - because it was necessary for the flight to eliminate the need for its passengers to stop or leave the carriage.
It’s very important, however, to note that even though the size of the coach and its amenities had an influence over the coaches speed, they were not the cause of the flight’s failure. The first stumbling block occurred when the harness of the carriage broke—bad luck and nothing unusual for travel at the time, but it caused a chain reaction. The mending of the harness caused the coach to become 2 hours behind schedule (it was already running late) which, in turn, caused the duc de Choiseul (who was waiting at a point with dragoons) to take his men back toward Montmedy, which meant that there would be no military escort waiting for them if (in reality, when) they needed it.