The growth of electrical energy in a thundercloud prior to a lightning flash can be studied by measuring the electric field. The use of airplanes to measure the electric field has been a problem because the intense electric field of a thunderstorm causes electric breakdown in air at sharp metallic points and edges. The electrical charge produced by the breakdown can be confused with the charge in the thunderstorm itself, causing large errors in the measurement. Electric field sensors on the fuselage of a single-engine airplane can give erroneous measurements when the electric field amplitude is as low as 10 kV/m. However, new electric field sensors in pods under the wings away from the fuselage appear to give correct measurements up to about 150 kV/m, the most intense field we have encountered. A flight around a rainshaft beneath a thunderstorm shows how the electric field, deduced from the new pod meters under the wings, differs from the field deduced from meters on the fuselage. ¿ 1998 American Geophysical Union