NTSC is based on a 525-line, 60 fields/30 frames-per-second, at 60Hz system for transmission and display of video images. This is an interlaced system in which each frame is scanned in two fields of 262 lines, which is then combined to display a frame of video with 525 scan lines. NTSC is the official analog video standard in the U.S., Canada, Mexico, some parts of Central and South America, Japan, Taiwan, and Korea.
Since NTSC is inherently an interlaced system (in fact, so are PAL and SECAM for that matter), since most displays were interlaced when DVDs came out, I assumed that all commercially made DVD movies were also based on interlaced video. Now, of course, many newer displays are natively progressive scan, as well as many newer DVD players; but I didn't know that they started making DVDs from progressive video, (though I admit it would now make sense to do so). Are you aware of any commercial DVD releases of progressive video? Or are you merely suggesting that it is a theoretical possibility?