We only live 10 mins from the airport
I suspect that’s one reason for some of the variations.
If I lived 10 mins from an airport, I’d leave it much later.
DH was posted to Germany for a few years, while I lived in the South West. I used to catch a 4.30pm flight from Stansted. If I missed the flight, that meant I couldn’t see him that weekend and it would be another 3-6 weeks before seeing him again.
It also involved a lot of motorway travel, around the M25.
So, I’d set out at 9.30am and get there, usually, by 12 noon. I’d park up, wander up to the terminal, get through security, get lunch, surf my iPad, relaxed knowing I was there and ready to go.
Once I got held up for 2hrs on the M25. Still made my flight.
I guess it’s all risk appetite, isn’t it? I’d be far more prepared to miss a flight for work than I was for a 36hr hook up with DH!