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In this question, Hephaestus Aetnaean posted the following cool movie:

which showed the following still:

enter image description here

As indicated by the red circles (the yellow marking can be ignored) there seem to be a few hotspots visible on the IR image. What are these hotspots? They seem to be rather random, so I'm not sure what they exactly are.

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    $\begingroup$ the one near the nose is a heated air data probe (see the video at 0:18) $\endgroup$ – Federico♦ Feb 17 '16 at 9:12
  • $\begingroup$ Sorry for the yellow spot, it was my first attempt to mark the spots, but I didn't found it obvious enough and couldn't be bothered to make a new screen capture :p $\endgroup$ – ROIMaison Feb 17 '16 at 9:16
  • $\begingroup$ The yellow spot is probably the sun reflection (yes I understand you painted it yellow, but its on the canopy where the sun would typically reflect). $\endgroup$ – Ron Beyer Feb 17 '16 at 13:54
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    $\begingroup$ The hot spot in the cockpit could be the pilot's cigar. $\endgroup$ – Mike Brass Dec 28 '17 at 0:39
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In this picture from Wikipedia it can be clearly seen that the two along the bottom of the fuselage are both heated air data probes, as Federico pointed out. The probes are heated to prevent ice from forming and blocking air flow to the sensors. The forward one is a pitot probe, and the aft one is a total temperature probe. The AOA sensor can also be seen as a much smaller hot spot above the forward pitot probe.

I agree with Ron Beyer that the top area is probably the sun reflecting off of the canopy. The lower area is probably a sun reflection as well, off of the external fuel tank. You can see in the video that these areas are not always visible, and move as the F-16 flies past, consistent with a reflection.

F-16 nose with areas circled

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    $\begingroup$ Good answer but to clarify the forward probe is only the Pitot probe. The static port is further back flush with the aircraft skin. They work together in the same system. The system itself is referred to the Pitot-static system. Just wanted to clarify it. $\endgroup$ – Mark Feb 18 '16 at 20:31
  • $\begingroup$ @Mark thanks, fixed. $\endgroup$ – fooot♦ Feb 18 '16 at 20:45
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I believe what you are seeing is the infrared image picking up heat sources. As the plane flies through the air friction is caused with any object sticking out from the skin of the aircraft. The nose of the aircraft has a Pitot tube which by design sticks out in the airstream. This causes a lot of friction. Additionally the pitot tube is heated to prevent ice from clogging the tube. As for the other spots, I am unsure as to the devices but they appear to be in the airstream as well. Perhaps some are small antennas.

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