I am American with a female gender United States Passport. I have travelled internationally on 3 continents entering and leaving several different countries since becoming full-time Jennifer with my female passport. I have never encountered any problems with my gender -- i have even travelled as Jennifer to an Arab Muslim country, Morocco. I have never had any issues with immigration or customs or security checks in any of several countries I have entered and left. Just standard questions an procedures that any international traveller does.
I have always been called "ma'am" by airport security, ticket agents, and immigration officials. Meaning, the equivalent of "ma'am" in the language of the country I was in -- so this has included English, French, Spanish, and Arabic.
I have not entered the United States for many years, so I haven't experienced the American TSA since Jennifer but I am a highly experienced international traveller and I have researched TSA so here are my feelings ---
My research shows that if you are a trans lady but don't have female gender "heavy" documents yet such as a driver's license or passport, then for United States domestic air travel you must buy your ticket under your male gender as shown on your government-issued ID.
If you have legally changed your name to female but you have not yet changed your gender to female (since gender change on official documents is usually harder to do than name change), then you must buy your ticket as shown on your government-issued ID = in this example, male gender and female name.
If your government-issued ID shows you as still male name and male gender, then you must buy your ticket as male name and gender, check in at the ticket counter using male name and male gender as shown on your government ID as this is current law in the United States. You may however dress fully female if you wish, and explain you are trans lady if you so desire.
When you get to initial TSA ID inspection point, my research shows that you must use your name and gender as shown on your ticket and government-issued ID. This might still be male, but you may dress however you wish as fully female if you wish.
If you have a secondary inspection or secondary pat-down, you have an absolute right under TSA rules to have a female officer do the pat-down if you are dressed and presenting s female even with male ID. It might help to have a doctor's or therapist's letter with you while you travel as additional support, indicating you are a trans lady undergoing gender transition to female. You should POLITELY ask to speak with a supervisor if you have problem. Never be rude yet stand your ground. There have been some nightmare TSA stories in newspapers so avoid problems be careful, polite, and insist on your rights.
Never accept a male officer to pat you down or touch your breasts when presenting as female, even if you still have male ID.
I hope this helps. If you have any more questions about this subject, please feel free to ask me publicly or privately.
I will also attempt here to post a photo of myself in the dress I usually use for travel.
Jennifer xx