Consider the following situation.
You have a ticket from airline A from airport X to airport Y, then another ticket (different PNR, airline B) from airport Y to airport Z.
The connection time in between flights is short, so can you ask check-in counter of airline B at airport X to give you the boarding pass for the second leg of your journey? Assume that you don't have any check-in luggage.
All the flights are international and you have all the required visas on your passport.