A Strange Phenomenon: Rainbow / Halo around airplane's shadow

[BIAD]

While travelling through plane today; I came across a strange phenomenon. The plane's shadow formed on the clouds underneath was surrounded by a rainbow/ halo. 

Further to that, the shadow was shrinking and expanding rapidly but the size of the halo remained almost same.

Intriguing Raman, but I wonder if the effect had anything to do with the glass it was being seen through?
That's the problem when filming through different materials, the clouds, the atmosphere and the aeroplane's
window. We need a scientist!!