I've no personal experience with this camera, but most have a diopter adjustment on the viewfinder to adjust the focus for your eyes. Did the photos come out sharp, or was it just what you saw through the viewfinder? If so, it's probably just the diopter that needs adjusting to your eyes.
As with many bridge style cameras, they are good at what they are designed for, but have their limitations, eg slow fucussing, noisy at low-moderate ISO, the large zoom range is a compromise on image quality, to name but a few. For static and slow moving aircraft in good light, it may do what you want but if you're interested in capturing aircraft in the air or in less than ideal lighting, you'll soon find it's limitations. It all depends what you intend on using it for.
Equipment: 2x Canon EOS 50D; Sigma 10-20 EX DC HSM, 50-500 EX APO DG, Canon 24-105 f/4 L, Speedlite 430EX