OK, OK, that's not that much.
US is a very densely populated area, and has lots of passengers. E.g., JFK-MIA, though domestic, is quite long flight. But look at this:
Iberia has been flying MAD-BCN-SVO & SVO-BCN-MAD for a while, and although it was a two-origin-two-destination flight (passengers from BOTH Madrid AND Barcelona to Moscow, or passengers from Moscow to Barcelona AND Madrid, you were able to fly MAD-BCN or BCN-MAD on regular scheduled flight on board a 742. Boarding-to-luggage claim scheduled time is 60 mins., but the effective time of flight is 30-to-35.
Further, in very crowded peak times, (such as late night of the last day of Easter Holidays) or minimum scheduled services of early mondays morning or late fridays evening during a strike, the Air-Shuttle between BCN and MAD has been serviced by IBE's D10s & 742s. (Although I have seen once the 727-200 usually in service carry... ONLY ONE PASSENGER!!!)