England Having trained on single engine aircraft, the squadrons's pilots were surprised to find Lockheed P-38 Lightnings sitting on Stoney Cross's dispersal pads. Only members of the advance party had any experience flying the Lightning. These pilots had flown combat sorties with the 55th Fighter Group. The change from single engine to twin engine aircraft required considerable retraining for both pilots and ground crew. Although some pilots entered combat with as little as eight hours of flying time on the P-38, in late April the squadron was reinforced by pilots who had trained on the Lightning in the States and were more experienced on the type. However, the lack of instrument training in the P-38 took its toll on the 394th as weather, not enemy action, caused the loss of pilots and airplanes. On 9 May, the squadron flew its first combat mission, a fighter sweep over Alençon. For the remainer of the month, the unit flew fighter sweeps, bomber escort and dive bombing, missions and suffered its first combat losses. On D-Day and the next three days the squadron flew missions maintaining air cover over shipping carrying invasion troops. These missions continued for the next three days. The 394th and other P-38 units stationed in England were selected for these missions with the expectation that the distinctive silhouette of the Lightning would prevent potential friendly fire incidents by anti-aircraft gunners mistaking them for enemy fighters. Shortly after the Normandy invasion, on 12 June, the 367th Group was selected to test the ability of the P-38 to carry a 2,000 lb bomb under each wing. The selected target was a railroad yard, and results were mixed. By mid June German ground forces had withdrawn to defend a perimeter around Cherbourg Naval Base, a major port whose capture had become more important to the allies with the destruction of Mulberry A, one of the artificial harbors constructed near the Normandy beachhead. An attack by VII Corps on 22 June was to be preceded by low level bombing and strafing attack by IX Fighter Command. Briefed by intelligence to expect a "milk run" The 394th flew at low altitude through what turned out to be a heavily defended area. Within two to three minutes after beginning the attack the squadron lost five pilots. Seven group pilots were killed in action. Nearly all surviving aircraft received battle damage and the entire 367th Group