The B-29 had a maximum speed of around 560 km/h (348 mph), and would attack in a cruise at about 360 km/h (224 mph) at 8,000-10,000 m (26,247-32,810 ft), an altitude where no current Luftwaffe aircraft was effective, and for which the only effective Wehrmacht anti-aircraft gun was the rarely-deployed 12.8 cm FlaK 40, which could effectively fire to an altitude of 14800 meters .