This is clearly a dangerous development.

The (London) Daily Telegraph reports:

Taliban militants have used a heat-seeking surface-to-air missile to attack a Western aircraft over Afghanistan for the first time.
The attack with a weapon believed to have been smuggled across the border with Iran represents a worrying increase in the capability of the militants which Western commanders had long feared.
The Daily Telegraph has learnt that the Taliban attempted to bring down an American C-130 Hercules aircraft flying over the south-western province of Nimroz on July 22. The crew reported that a missile system locked on to their aircraft and that a missile was fired.
It closed in on the large C-130 aircraft, pursuing it as the pilots launched a series of violent evasive manoeuvres and jettisoned flares to confuse the heat sensors in the nose of the missile. Crew members said that they saw what they believe was a missile passing very close to the aircraft. The C-130 was not damaged in the attack.

NATO officials, however, are keeping their silence:

“If there was such an incident of the type you describe in Nimroz it is classified,” said a NATO spokesman. “I can’t release it, if in fact it did occur.”