The present application is directed to dielectric isolators for use in aircraft fuel systems to control lightning induced current and allow dissipation of electrostatic charge. The dielectric isolators are configured to have a high enough impedance to limit lightning currents to low levels, but low enough impedance to allow electrostatic charge to dissipate without allowing buildup. Although the dielectric isolators may develop a potential difference across the dielectric length due to the effects of lightning currents and its inherent impedance, they are configured to withstand these induced voltages without dielectric breakdown or performance degradation. In one embodiment, the dielectric isolator includes a tube constructed of a composition including a thermoplastic organic polymer (e.g., PEEK) and carbon nanotubes, and a pair of fittings attached to opposing ends of the tube. In another embodiment, the dielectric isolator includes a tube, an outer annular portion, and an interconnecting web, each constructed from the composition including a thermoplastic organic polymer (e.g., PEEK) and carbon nanotubes. This later embodiment is an integrally formed one-piece structure. The dielectric isolator is capable of exhibiting an electrical resistance from about 105&OHgr; to 108&OHgr; at an applied potential of greater than 500 volts DC when measured from one fitting to the other fitting.