Goodyear's Pilgrim, built in 1925, was the first commercial non-rigid airship flown using helium. With a landing wheel replacing bumper bags and the first passenger car held flush against its bag by internal cables, Pilgrim's contributions to aeronautics were recognized by the Smithsonian Institution, which exhibited the airship as a milestone in aviation progress. The mast, called a belly mooring, was an experimental portable design developed in 1930 to enable cross-country operations independent of permanent hangars.