The Egan brothers expected somebody to develop a medium-size air vehicle like the PLIMP Airship in the 1980s or 1990s, but nobody did. Over time, they kept their eye on the news, occasionally visited the library to look for an announcement of this type of development, and saw nothing. So they decided to investigate the idea themselves.
In 1999, they hired an engineer to assess the possibility of building and flying the vehicle, and the report said it was impossible because:
As a result, of the Engineers assessment they put the idea on hold—until in 2012, they requested another report, which said their idea might be viable in three to six years. That was all they needed to hear—they immediately got to work on solidifying their concept.