>>2877222
>sneak up
As a status holder in two OneWorld airlines, there is no such thing and pretending it exist will get you laughed at by gate agents, ticket agents, and FAs. If you actually attempt it, it will get you arrested for not following crew instructions (rightfully so) and face lifetime bans from airlines.

The closest analog is FA denying status holder upgrade (either complementary or certificate-based) from lower class of service into premium cabin because a non-revenue passenger (read: employee or family) is inappropriately prioritized.

Fundamentally, cash is king and money talks for everything in finalizing who is upgraded if any. When premium cabin is not booked and sits empty, all airlines go through a strict hierarchy of paid upgrades > instrument-based upgrades > miles upgrades > status holder complementary upgrades (start with invite-only status, go level by level down to lowest). If you're not paying one way or another, you don't have a chance in hell.

>>2877222
>managed to sneak up
that's not a thing

in the good old days(TM) you could asked nicely
but that stopped working >10y ago

or if some staff had pity
I flew a lot as kid / teen (parents moved for work, I stayed for school) and got upgraded pretty regularly to business / first class
although sometimes my parents booked business class directly

>without paying more than double to price of a plain ol' economy trip?
status
had the Lufthansa Senator status basically my whole (adult) life (well it's actually for lifetime now)
and you sometimes get upgraded
but that only happens on tourist heavy routes during vacations, when economy is overbooked
so don't expect it

Check to see if you can upgrade your seat about a week before check in, it only really works with low demand flight routes though. Ive gotten 3 hour first class flights on Delta for $40 before.

>>2877222
I saw a gypsy try this on a train in Romanian and they immediately booted him out