The 14 new Boeing 777-300s United Airlines expects to receive this year have started arriving with the airline's new lie-flat Polaris business class seat in front and the tighter 10-seat layout in the back. United also is adding the extra seats on 19 of its older 777-200 aircraft that came with a nine-seat configuration, but hasn't said whether it plans to make similar changes to the rest of its 777s.