Originally Posted by
tsastor
I am frequently checked for passport when boarding the plane, not only at check-in. Not sure they check visas though.
And airlines letting people without valid documents travel are, when caught, required to fly these people back at their cost + probably fined. So yes, they are entitled to deny boarding for this reason.
Passports checked? Frequently for intra-Schengen international travel too. Visas checked for same kind of travel? Very infrequently (even by airlines). [For a large proportion of my international intra-Schengen travel, passports aren't even generally required for travel; and in some cases no ID whatsoever is required for a substantial chunk of passengers engaged in cross-border intra-Schengen travel, even by air.]
Your latter paragraph above doesn't exactly hold up as probable or even necessarily lawful under various arrangements, applicable to intra-Schengen travel amongst a multitude of Schengen countries, EU and otherwise, as long as a passport is used for travel.