Dennis Hope brings to Stillwater a corporate attitude, a cutthroat business mentality that prioritizes creating profit over creating art. When he first suggests that Stillwater use an airplane to help them play more shows and make more money, the band is wary. "Doris is the heart and soul of this band," Jeff Bebe says of the beloved Stillwater bus. The band succumbs to the pressure, however, ultimately replacing Doris with an airplane.
Of course, it's in this very airplane that the band's most contentious moment occurs. When they hit an electrical storm mid-flight, everyone believes that death is imminent, and relationships disintegrate in a hurry. Watching the band unravel before his eyes, Hope makes it heard that he is quitting. Now, the plane lands safely, of course, and everyone makes it out alive. In total shock and with wounded pride, though, it's unclear, if Stillwater will survive.
The airplane is the physical representation of Hope's money-first, corporate mentality. Stillwater, in having to deal with these pressures, loses sight of the very reason they started playing music in the first place: their love for rock and roll. It's no coincidence that the airplane itself almost brings about their demise.
In the movie's final montage, we see that Stillwater has rejected the airplane in favor of their old bus Doris. This means that they've also rejected Hope and the exploitation of rock and roll for which he stands. On "No More Airplanes Tour '74," we know that Stillwater is once again making music for the love of it.