My experience of diabetic meals on flights was that they were quite often the sort of dish where you can't separate the carb so easily, for example paella (very tricky), lasagne (very messy). I've actually been on one flight where I had the diabetic paella and everyone else had sandwiches, I've never had so many admiring glances and inquiries as to why I wasn't eating sandwiches like everyone else. US internal flight where people seem keener to see what you're doing.