I’ve flown with the US many times this past year and I was never asked to show proof that I was diabetic. I brought a medical note from my endo just in case, but was never asked to show it. I carried my syringes, insulin, meter, etc in my purse and was never asked to prove what it was. When I put my purse through the metal detector, I took out my diabetes supplies to be scanned separately and I’ve never been asked for them to be confiscated.
I would second the suggestion to bring a few snacks (pre packaged) on the plane because I was in an instance when we had delays for over 6 hours and I had to go and purchase at the terminal. But, there have been issues lately in the news about sometimes being delays for take off and landing and them not allowing the passengers off the plane. So, be prepared. (They will not allow drinks, that I’m aware of- except if you use Pavlos’s idea to inform them that you’re diabetic. My diet soda and regular soda were confiscated at security check point)
When I was on the pump, they didn’t ask questions. The security guard just wanted to be shown what it was and where it was hooked up to my body and that was that.
There is a separate metal detector in the security that people with medical devices go through (at most airports) and it tends to be much quicker than the general security anyway. If you’re in that security line, they don’t usually give a lot of hassle to special needs because they are expecting it.
When on the plane, my BG tended to go high. Stay hydrated and keep checking your BG while in flight. Also, you may notice your knees and joints aching for a little while after the flight. Diabetics tend to water retain, so you may feel a little “out of sorts” for a day or two after the flight.
Good luck and safe travels!