I have twice; once flying to Italy in the lav. Embarrassed when we left & got funny looks and stares from the folks waiting. I said that "he (my bf at the time) needed help" and just kept walking. I was wearing a denim skirt and removed my panties first.
Second time was in the rear of the plane, across four seats flying back from Rio, under blankets, pretending to be sleeping. Planes are not empty like this anymore!