Yes, you can escape from the knee-crunching confines of regular economy class. And you can do it without raiding your financial portfolio to pay for first or business class. Several big North American airlines plus KLM offer "semi-premium economy," or several rows of regular economy seats with added legroom.
You generally get the same cabin service as regular economy, with a few extra perks on some lines. As an ordinary traveler, you can buy your way into these extra-legroom seats when you reserve your ticket or just before departure, on a standby basis. If you're a high-ranking frequent flyer or you paid full-fare economy, you might get in for nothing extra or at a discounted price.
(Sample fares listed are based on a comparison for midweek flights in February 2013. Seat measurements were found on SeatGuru or the airlines' websites.)
United has installed Economy Plus seating on all pre-merger mainline planes and expects the installation on former Continental planes to be completed by the end of 2012. The seat pitch is 34 to 35 inches, compared with the regular pitch of 31 to 32 inches.
Economy Plus adds no extras. United pioneered the idea of semi-premium economy in North America, and its long-haul planes typically have at least twice as many semi-premium seats as other lines' similar planes.
Sample Price: The base economy fare between Boston and Los Angeles is $338 round-trip; Economy Plus adds $79 each way.