Markit wroteSo really it's in yours and their best interests for you to have some proof of an onward journey - valid or not, the airlines will consider the validity of your onward ticket your problem and are largely dis-interested in it once proof has been made.
If, as suggested elsewhere, you photoshop an old onward ticket and it's spotted on arrival as fake, the airline has NO responsibility for your return. That's when you may end-up in the airport pokey till you buy an outbound ticket....if you're lucky.
