A civilian Cessna does not have a weapons lock indicator as heard at the end of the episode. Although there is some possibility this plane was some special issue government plane intended for flying into foreign or potently hostile airspace it is very unlikely.
The radar screen Jake is looking at while flying the Cessna is a ground based radar. Aircraft doesn't have rotating antennas and no civilian aircraft has 360 degrees detection. It can't be a modified plane either because it'd still need a rotating radar dish or something.