Yes, but the rebels were extremely lucky with that. What basically happenedwas some Y-Wings got in a few shots on the bridge deflector shield generator, and the A-Wing that crashed into the bridge was hit by enemy turbolaser fire. In all other situations, that would be enough to destroy the fighter outright, but the thing managed to maintain structural stability, and made a one in a million crash landing into the bridge of the Executor.
Like i said, LOTS of luck was involved.
And the Executor had been the primary target for the entirety of the battle so its shields had been shot up like crazy. They y-wing strike managed to knock out the sensor domes and overload shield systems, boom.
Now back to your regularly scheduled programming...