Airco DH4 & DH9: The Fast and Flawed Bombers of WWI That Shaped Future Designs The Airco DH.4, first flown in 1916, was a powerhouse of its era, reaching a blistering 143 mph and often outrunning enemy fighters. However, its design was flawed, placing a massive fuel tank between the pilot and observer, making communication nearly impossible. Its successor, the DH.9, debuted in 1917 aiming to fix these issues but was hampered by unreliable, underpowered engines. Despite these setbacks, both aircr