Is it cheaper to buy better flight seat now or upgrade on the day?

[alexxturnerr]

I'm planning a solo trip for next year, it'll be my first solo trip and it'll be taking place during my birthday so when I fly I wanna be extra comfortable.

Is it cheaper to buy a better seat when I'm booking my holiday or is it cheaper to upgrade on the day?

 

[BudgieMama]

It might depend on whether there is anything available on the day... I had a serious problem with my seat on my flight home, and when the cabin crew looked at moving me, there was not a single seat, anywhere on the plane in any class that was free. If you want to guarantee one, I'd book it in advance

 

[cheryl.UK]

When they have sales, it's cheaper than on the day often.