I haven't been to any of those airports, except for Lisbon. Didn't see any front and back boarding in there. Neither in BCN, MAD, LHR, LGW, IST, or AMS. I have

I haven't been to any of those airports, except for Lisbon. Didn't see any front and back boarding in there. Neither in BCN, MAD, LHR, LGW, IST, or AMS. I have boarded and de-boarded from the back (but not from the front) in a handful of smaller Spanish airports, though. In the US, I would say that it is not usual at all, or I have been to the wrong airports (IAD, DFW, AUS, IAH, SFO, LAX, JFK, LGA, CLT, ORD). I haven't seen this either in Asia. Perhaps this is highly airport dependent? Still, I would think that this is far from common.