Sky was not yet black. Still dark blue with sun's rays shining up from just below the horizon. ( couple reflections on the plane ) The plane was so high I couldn't see it with the naked eye...only the contrails. Canon FDn 300mm lens + Canon FD 2x multiplier for 600mm total, on an NEX-7. Very difficult getting on / staying on the jet as it passed through the field of view so fast.