"Wooden Airfield" joke

An enemy decoy, built in occupied Holland, led to a tale that has
been told and retold ever since by veteran Allied pilots. The German
"airfield," constructed with meticulous care, was made almost
entirely of wood. There were wooden hangars, oil tanks, gun
emplacements, trucks, and aircraft.
The Germans took so long in building their wooden decoy that Allied
photo experts had more than enough time to observe and report it.
The day finally came when the decoy was finished, down to the last
wooden plank. Early the following morning, a lone RAF plane crossed
the Channel, came in low, circled the field once, and dropped a
large wooden bomb.