a commercial airplane descends toward the runway with its landing gear fully extended. The aircraft's wheels make contact with the asphalt as small puffs of smoke appear from the tires. The plane's nose gradually lowers as it settles completely onto the runway surface. Ground crew members with safety equipment watch from the sidelines, some pointing toward the aircraft. Airport vehicles wait nearby to guide the plane to its gate. the exact instant when an aircraft lands and settles on the ground