Any first hand experience on how strictly this enforced at BCN? My (basic) fare includes underseat bag but any cabin bag needs to be checked in (FOC) at the check-in counters. My small backpack may exceed the allowed dimensions for an underseat-bag a bit (not much, difficult to spot I guess) but for several reasons I would prefer not to check it in (although this is free of charge). I would also hate to be singled out at the gate and having to pay 25 Euro and getting my backpack in the hold.

FYI I travel with Ryanair extensively and my backpack has never been an issue there; FR only seem to focus on trolleys that some pax try to take onboard (without paying for Priority and 2 cabin bags) whereas normal backpacks are not an issue.

So the Q is if Vuelling is different than FR in terms of normal backpacks/enforcing the underseat-bag dimensions at BCN?

PS I am aware of that I'm able to add and pay 10 Euro in advance for a cabin bag; but that is not my Q.