Flying whilst pregnant...

Hello! First post here, you all seem like a lovely bunch :-)
​This is a bit of a premature question as I'm not pregnant (yet). 
​We are trying for our first baby and I'm wondering what the latest is that any of you have gone on holiday abroad?
We were hoping to go away with friends for a weekend in September but if I were to get pregnant next month (here's hoping), in your opinion would I realistically be too worn out at that stage of pregnancy to be flying to Europe? I've read that you can fly up to 28 weeks pregnant but as I've never been pregnant before, I wonder if I'd be too tired?