On a fine early morning, when the flight from Bangalore International Airport to London – Heathrow, climbed up the heights, I could see this Circumhorizontal Arc. (Look at the upper right-hand side of the first picture and slightly towards left from the center of the second picture to spot it.) But I am not sure if it is a Circumhorizontal Arc, or a sundog. The Wikipedia definition says that “a sundog is an atmospheric phenomenon that creates bright spots of light in the sky, often on a luminous ring or halo on either side of the sun”. You can read more about sundog in http://en.wikipedia.org/wiki/Sun_dog.Circumhorizontal arcs or fire bow are formed not from water droplets in sky, but due to the presence of ice crystals in sky in the form of Cirrus clouds. More info about Circumhorizontal arcs is available at wikipedia => Circumhorizontal Arc
Here is another similar optical event that I captured long back ago that looks like a Circumhorizontal Arc =>A Rainbow or a Circumhorizontal arc!!! and here is yet another capture that I made a while back that looked like a Sundog =>Parhelion