Optical effects seen by Rose Babcock on a flight from Victoria B.C. to Edmonton, Alberta, Canada. ©Rose Babcock, shown with permission
At top - Small spherical water droplets in the clouds diffract and backscatter sunlight to form a multi-ringed glory.
The glory is directly opposite the sun and therefore surrounds the point where the shadow of Rose's camera would appear in the sky had not the airplane shadow got in the way.
Middle - Spheres of water 10-1000X larger than cloud droplets - raindrops - refract and internally reflect sunlight to form primary and secondary rainbows. Here they are separated by a noticeable dark space, Alexander's Dark Band, where the drops refract no light towards the camera (but those drops do form someone else's rainbow).
Lower - Untold millions of cloud water droplets are collectively so opaque that they cast giant shadows - crepuscular rays and shadows - downwards through the air. In this picture it is obvious that the shadows are tangible entities that could be flown around or through.
Next time you are faced by an airport's impersonal check-in machine, try to persuade it to deign to allocate you a window seat. There are many sights to be seen.