I have many holiday experiences being a type 1, so have some useful ancedotes that i have gathered over time!
Firstly, always make sure that you have back-up kit. We normally divide my medication between all of our cases - in case a bag goes missing, and between our hand luggage.
Also, british airports are normally very good, but do just tell the people at customs, before the bag is scanned, "my daughter is a type 1 diabetic so her medication is in this bag". Don't be surprised if they do quickly check your bag after's it been scanned; nothing to worry about, and they're really nice about it. Just generally with all of this though, as someone who is diabetic - I just like everything to be as normal as possible. With customs and everything, sometimes my dad especially can get quite panicky, and I personally always fee much better travelling, when it's just 'something i have to do' - my dad literally is like screaming at the security guard "she's diabetic!".
Also, sounds obvious, but for hypo corrections during the flight, make sure you take food as opposed to drink - one time my mum packed juice, we got it confiscated at the check-in desk and i had a hypo - not the best start to the holiday!
And like other people have said, always have food supplies with you - especially somewhere like Egypt, where the food wasn't always great for me. It's also worth putting a packet of digestive biscuits in the case, just as back-up food. *Also, sometimes the hotter climate can cause hypos; it does for me anyway - the doctors says it's something about the speed at which the insulin works? So yes, just keep testing.
Final point: with regards to supplies, literally take about 3x more than you need! We were in New York when the volcanic eruption happened two years ago, and it was literally a nightmare as we nearly ran out of supplies. Especially with somewhere like Egypt, where there won't be supplies there (at least we were in America). Yes, just take loads of supplies - nothing to lose by doing so.
Hope I've helped. This is all really from personal experience. My main thing would be to just enjoy it, and don't make the diabetes a big deal - I always like things to be as 'normal' and as calm as possible on holiday. But at the same time, do test frequently- the last thing you want is hypos or hypers affecting the holiday.
Have an amazing time!
Sophie