The T-47 Airspeeder also known as the Snowspeeder, became one of the rebel alliance's most prized weapons after their success at the battle of Hoth.
The Airspeeder was modified to cope with the extreme weather of Hoth. They are the only units that pose a direct threat to the AT-AT's. They can fly around the AT-AT's legs and attach a harpoon cable to the legs. They then have to fly around the legs three times to destroy the AT-AT. The AT-AT can blast the speeder as it circles the legs, and move ahead far enough to have the speeder crash into its legs or walk close enough to the other AT-AT that the speeder crashes. The Snowspeeder is also a fast means to get across the field.