<p>Within a few short months, the Ninth built from a new organization to the largest tactical air arm in the war. By the date of the invasion, Ninth AF had on hand about 4,500 tactical aircraft of all types and about 2,700 gliders.
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<p>The air attacks in support of Overlord began on schedule, 50 days before the landings. The primary target was the Luftwaffe. A vitally important secondary mission was a thorough photo-reconnaissance of the coastal areas. Then, on D-Day minus 30, the target list was expanded to include the transportation networks, the coastal defenses, and potential Luftwaffe bases within a 130-mile (209-km) radius of the landing beaches.
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<p>The Ninth AF was most heavily involved; the other air forces were still employed against strategic targets deep in the Reich, and against the Crossbow sites. As the target list grew, the Ninth was joined by the Eighth and by the RAF, whose Second Tactical Air Force was a powerful addition to the air strength.
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<p>By the end of April, a dozen major rail centers had been blasted into a rubble of twisted steel, mangled rolling stock, and demolished buildings. The Germans countered by concentrating their anti-aircraft artillery at the railheads, and by fast repair of trackage breaks. By the end of May, although even more railway junctions had been put out of action, the expected breakdown of the system had not yet been achieved.
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<p>Strafing moving trains had not been condoned because of the danger of killing civilians, but the trains had to be stopped, so the fighters were turned loose. The first of these Chattanooga Choo-Choo missions on 21 May sent 763 AEAF fighters over northern France and 500 Eighth AF fighters over Germany, with orders to shoot up any train anywhere. Within a few days, daylight train movements stopped dead, halted by the simple interdiction tactic.
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<p>On 26 May, Ninth AF B-26s struck for the first time at the bridges on the Seine. Before the invasion forces landed, every span downstream of Paris had been cut, in a major contribution to stopping the movement of German reinforcements.
