air travel

20-30 years ago this used to work. Source: I did it myself, and approximately a quarter to a third of the time it worked. You could turn up at check-in, smartly dressed (apparently that mattered then) and ask if there were any spare seats in business class, and miraculously occasionally you were upgraded for free. Similarly hotel upgrades (that still works occasionally) - I'd get an upgrade to a suite by asking, though the particular hotel I visited so frequently they knew me by sight and that might have had something to do with it.

Now, well, you can ask, but you are very unlikely to be successful. Firstly, airlines load plan a lot better. Secondly, if airlines have additional space, they will be happy to sell an upgrade at the airport. BA have a program called Airport Upgrade (AUP) and their checkin staff are heavily incentivised to sell them to you - given that, why would they give them away? Some airlines allow miles/points earned to be redeemed for upgrades in this way. Thirdly, airlines will on occasion provide operational upgrades (OpUps) - but these in general happen only when one class is oversold and they have to upgrade someone. Note "oversold" can include "sold the right number of tickets but one seat has broken" and "needed a business class seat for a resting crew member" (leading to an upgrade to First). The person they pick is relatively carefully selected (for instance favouring frequent flyers, or someone who has not flown business before and they think might fly business again if exposed to it) - but even if you don't believe in the magic of their upgrade algorithm, the point is that they select the OpUp, and it's not given by asking

That said, no harm in asking nicely so long as you don't mind being disappointed.