The Patriot is RADAR guided, not a heat seaker. They crew involved did not expect to get shot down, and knew they were over 'friendly' airspace, so did not react to the warning from the aircraft, as they expected it.

That incident was an equipment failure, and a comms breakdown by the American guys. Both lessons now learned.

The new DIRCM system is not yet available on all aircraft types - it's too new!
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