Final answer:
The type of cloud typically associated with lightning when flying in an airplane at high altitude is the cumulonimbus cloud. These clouds are known for severe weather conditions, such as thunderstorms, which include the lightning you see from the plane.
Step-by-step explanation:
If you are flying in an airplane at 36,000 feet above sea level and you see lightning outside your plane window, the type of cloud that is close by is most likely a cumulonimbus cloud. Cumulonimbus clouds are associated with severe weather phenomena such as thunderstorms and lightning. They are towering clouds that can reach from just above the Earth's surface to heights well into the stratosphere, which is where you would be flying. The presence of such a cloud indicates that there is enough atmosphere instability and moisture to produce the thunderstorms and lightning you're observing.
Other cloud types, such as cumulus, are typically associated with fairer weather and wouldn't be responsible for lightning. Altocumulus clouds, which are mid-level clouds, and cirrus clouds, which are high-level clouds composed of ice crystals, do not normally produce such weather phenomena. Stratus clouds, known for their blanket-like formation, also do not result in lightning.
Learn more about Cumulonimbus Clouds