Farnborough This week the Reg flying car, killer robot and general military crazytech desk has been attending the Farnborough Airshow. One of the show's highlights this year is the reappearance of the US F-22 Raptor ultrafighter, previously seen publicly in the UK for just one brief Monday display at Farnborough '08.

This time the Raptor, generally judged to be the most dangerous, most capable and surely the most expensive fighter plane in the world, will be appearing every day including the public days this weekend.

One of the Raptor's many high-tech features is its Stealth design. In large part this is about making the plane not invisible, but less visible on radar - a matter mostly of its shape and also somewhat of coatings applied to its exterior.

Another and less well-known aspect of stealth is the effort to reduce an aircraft's infrared emissions, to prevent its being picked up by infrared search-and-track (IRST) systems or the seeker heads of some types of missile.

This might seem impossible on the face of it, as a jet fighter naturally generates colossal amounts of heat in operation. But in fact the latest US Stealth fighters, the Raptor and the newer F-35 Lightning II, can reduce their infrared emissions noticeably under some circumstances - by dumping excess heat into the fuel in their tanks, so cooling their hotter parts and transforming the plane into a "flying thermos bottle" as the jargon has it.

Naturally, heating up a tank full of jet fuel is a dangerous business - a tank of aviation juice is unpleasantly akin to a flying bomb ordinarily, without boiling the fuel to boot. This is just one more reason why stealth planes are so expensive.

As the vid above (courtesy of Flight International and infrared-scanner maker FLIR Systems) shows, the F-22 can't stay stealthy in the infrared while performing an airshow routine - but you wouldn't expect that. The Raptor is performing some amazing stunts above the crowds at Farnborough this week - balancing on its tail supported solely by jet thrust, for instance, which it can do as it can swivel its exhausts (not as much as the F-35B jumpjet, which can hover in a normal horizontal attitude; the Raptor's vectored thrust is for use in air combat, not landing).

Full-power manoeuvres naturally produce flaring infrared signatures: but from some directions, in some parts of the vid, the F-22 does seem to be cooler than you'd expect - even though it probably doesn't have its IR stealth systems turned on. It's an interesting watch, anyway.