Nice list! The Cessna 172 is the very reason why I said there ought to be a separate list for general aviation, because in my opinion, aircraft like the Beechcraft Bonanza, Cessna 150/172, Aeronca Champion or Piper Cub have contributed a major part to U.S. aviation history. A few comments on Mr. Gubler's list:
- I pretty much agree with your assessment of the V-22. What has it done, indeed? That's why I thought the Sikorsky S-70 Blackhawk (H-60) was a more representative rotorcraft which has been the backbone of rotorcraft in the 1980s, 1990s and 2000s. The Huey was also in my list, a milestone if ever there was one, and a type that spans five decades in all its versions!
- The Jenny is an excellent addition, and the Curtiss buff in me hates himself for overlooking it! Both as a war aircraft and as a barnstormer, it probably captured the imagination of the post-WW1 generation more than any other airplane.
- I am surprised, however, that you should not consider the Bell X-1 as a major milestone, but well, it's your choice! Perhaps you'd see the Airacomet, Shooting Star or Sabre as more important in taking the US into the jet age?
- Why the B-29 and not the B-17? (or the XB-15 for that matter, the initial "Flying Fortress" that set the pace for all large bombers to come).
- The SBD was a potent aircraft, so was the Helldiver... but certainly the P-40 or the P-51 were greater milestones of WW2.