NACELLES CONTRIBUTE TO LIFT - THIS LIFT IS MEASURED DURING A WING DEVELOPMENT PROGRAMS IN WINDTUNNELS - THE AERODYNAMIC SHAPE OF THE 737 NECELLE IS NOTHING MORE THAN A FLAT ON THE BOTTOM FOR GROUND CLEARANCE - I BELIEVE THE 737 NG Clearance is something like 16 inches - not much for a crab manuever ! Nacelles are very expensive parts & lifiting nacelles are very complicating parts - IE if you want a nacelle to product lift - why not just add a bigger wing ? Lifting nacelles complicate the hell out of engine mounts etc. - therefore - it is not something being pursued because it is just easier to make a better wing & try to make the nacelle not hose up all that delightful development on the wing's aero - my 2 cents .. Lifitng nacelles have been explored - but the non symettrical shapes IE two halves of the nacelle are not the same - double the cost of manufacturing & sparing. Look at AIRBUS - both halves are interchangeable - IE cheaper to make & cheaper to spare - only need to keep one universal part instead of a left & right hand part ..