I would recommend disclosure. If you take a worst case to it's logical conclusion, what could happen?

-You lie, get hired at a US company. Happy day!

-Move to US and have a great time at the new company.

-Someone who knows you knows about the DUI and the fact you didn't disclose (ex-spouse, ex-friend, neighbor, etc). They make an anonymous call about the incident.

-You get fired years later for not disclosing.

-You're out of your old job and out of your new job and good luck when you try and get an airline job afterwards.

-Why did you leave your previous carrier? Well, I lied and didn't tell them I had a DUI 20+ years ago...

I don't know how the European judicial system works, but my suspicion is that there is a record somewhere on a computer somewhere that would prove that you had this DUI at some point, thus plausible deniability is out.(if there's no way to possibly track this in the sys If it can be tracked back to you, think it will be tracked back to you and lying is the kiss of death at most jobs; lying about a DUI would probably be considered un-hireable in the future, but I guess that depends on how much risk you are willing to take.