A few weeks ago while returning from a business trip I finally realized a goal to fly wearing flats (rest of clothing in male mode). At the airport I swapped shoes and put the other shoes in my luggage (gulp - dropping off the suitcase at check-in was a bit nerve-wracking - after that I was committed until I picked up my luggage).
It was nice - easy to get shoes off in the security line and more comfortable in the airplane.