Allied pilots soon found that the only reliable way to destroy the jets, as with the even faster Me 163B "Komet" rocket fighters, was to attack them on the ground or during takeoff or landing. Luftwaffe airfields identified as jet bases were frequently bombed by medium bombers, and Allied fighters patrolled over the fields to attack jets trying to land. The Luftwaffe countered by installing extensive "Flak" alleys of anti-aircraft guns along the approach lines to protect the Me 262s from the ground—and by providing top cover during the jets' takeoff and landing with the most advanced Luftwaffe single-engined fighters, the Focke-Wulf Fw 190D and (just becoming available in 1945) Focke-Wulf Ta 152H. Nevertheless, in March–April 1945, Allied fighter patrol patterns over Me 262 airfields resulted in numerous jet losses.