This is what would happen to you:
1. The aircrew would tell you everything is fine and totally ignored you after landing. And you got no compensation from the airline.
2. The custom control would hold you in a small black room from 12 hours to 7 days, along with all kinds of illegal immigrants.
3. Usually you would end up getting expelled to your passport's country, with it recorded on their system and even stamped on your passport, which means it will become much harder for you to apply for a visa.