Early airships were pulled down and held by a large ground crew, a pneumatic bumper bag on the car cushioning its landing. Today’s ships land on a swiveled wheel, roll up to a mast—or taxi off across the airport like an airplane and take off. These, however, are merely flight factors. More important is it that the wartime blimp was to a large extent hangar-bound. It could go no further from its base than it could safely return before its fuel was exhausted. Today’s ships are expeditionary craft, can go almost anywhere, stay as long as they want. They are no longer land-bound, can be refueled and reserviced at sea. They are much safer, rank high in this respect among all carriers whether on land, sea or in the air. Three independent lines of study contributed to these results, those of the Army, Navy and Goodyear, each free to follow its own ideas, to observe results found by the others, adopt them, use them as starting points for further developments, or discard them. The improvements were achieved in a relatively short period. The army started in after the war and carried on a continuing program till 1932. The Navy, absorbed in its rigid airships, did not get into non-rigids till the early 1930’s. Goodyear built the Pilgrim in 1925 but its development program really began with the blimp fleet in 1929. Noteworthy improvement was found during this period in materials, structure, design, engines and radio communication, with outstanding advances along three major lines. First was increased safety, permitted by helium gas. Wartime airships used hydrogen because it was all they had, had to develop what protection they could against fire through construction devices and operating technique. Hydrogen was not only inflammable, but under certain conditions explosive. World War pilots had to fly their hydrogen ships through thunder and lightning storms, dodge inflammatory bullets if they could. Zeppelin sailors wore felt shoes, with no nails to create a spark, used frogs for buttons, had to guard against static. It was a fortunate thing for the airship world when a gas was found in 1907 in Dexter, Kansas, which would not burn. Curious scientists, asking why, found it was helium, a gas previously identified (in 1869) only in the rays of the sun. Helium gas is inert, refusing to combine with any other element, does not deteriorate metal or fabric. It was not much heavier than hydrogen, the lightest of all gases, so proved a welcome gift to lighter-than-air. For some reason, not explained except on the theory that Providence takes special interest in America, helium has been found in quantity only in this country. It is a component, present to the extent of two or three percent in certain natural gas, though ranging as high as eight or ten percent in favored areas. It can be separated by compression and liquefaction from the natural gas,—which is that much improved by the removal of the non-inflammable content.