It was almost diamond shaped with dark sides reflecting sunlight from the west moving slowly from west towards south east. it was evening around 5:45 or 6:00 pm. the movement was slow and gradually it disappeared towards south east.
i was actually observing aircrafts coming in to land at delhi airport from my balcony. aircrafts pass at a distance of 3-4 kms away at an altitude of around 2,500 feet when i observed this strange object moving slowly a little far above may be around 4,000 feet. it gained altitude slowly and disappeared. i was able to observe it for around 20 minutes.