1. An ultrasonic diagnostic imaging system which produces an extended field of view (EFOV) image comprising: an ultrasound probe including a two-dimensional array transducer which may be moved along the surface of a subject; a beamformer coupled to the array transducer which controls the probe to repeatedly scan a plurality of intersecting images in image planes of two different plane orientations with respect to the array as the probe is moved along the surface, a first plane orientation being an S plane which is substantially aligned with the direction of transducer motion and a second plane orientation being a T plane which is substantially transverse to the direction of transducer motion; an image processor responsive to signals received from the array transducer to form sequences of images of the two different plane orientations as the probe is moved; a motion estimator, responsive to at least one of the sequences of images which produces estimates of probe motion; an EFOV subsystem responsive to the probe motion estimates which operates to produce an EFOV image from at least one of the sequences of images; and a display responsive to the EFOV subsystem for displaying the EFOV image.