He uses the same technique whenever a girlfriend says, "... I'm late."
After that moment, Ethan Hunt spends the rest of the franchise slowly backing away from tactfulness like it's a drunk 9/11 truther at a dorm party. Each new action becomes more and more high-profile as he opts less and less to use the ever-helpful face-disguising masks in their most needed moments. By the end of the first film, Ethan has successfully shown his face to a train full of civilians before blowing up a helicopter and nearly crashing into the conductor.
It's such a horrific event that we immediately see it on the news in the next scene ...
"A crash happened. And now, sports. Sports happened."
... where Ethan and his friend are toasting a job well done and listening to The Cranberries.