During the war, the Iraqis constructed a few quite clever ambushes for roaming helicopters- usually involving placing a choice target like a tank in an appropriate place, waiting for the helicopter to come near enough, and then letting off a barrage of practically everything- small arms, RPGs, AA fire, and even mortar fire.US loses two aircraft over Iraq
Helicopters constantly back up ground operations in Iraq
The Pentagon has announced the loss of an Apache combat helicopter over western Iraq, saying it was apparently downed by hostile fire.
An F-16 warplane also crashed south-west of Baghdad with the cause of the accident still under investigation.
The two-member crew of the helicopter and the F-16's pilot were not injured and were rescued by coalition forces, US Central Command reported.
American forces carried out raids targeting elements loyal to Saddam Hussein's ousted regime on Thursday while reports have been coming in of violent clashes in the northern city of Mosul.
Pay protest
Unconfirmed reports say a number of people may have been killed or wounded as hundreds of Iraqi ex-soldiers demanding their army pay clashed with police guarding Mosul's administrative buildings.
Witnesses who spoke to AFP news agency said that US helicopters circled above the city as the soldiers traded fire with the police.
The unrest apparently erupted after the local government began paying April salaries to civil servants but refused to pay ex-members of the Iraqi forces.
On the loss of its helicopter west of Baghdad, the Pentagon said two other Apaches had engaged "irregular forces" in the crash area.
They said the F-16 crashed at 0630 local time (0230 GMT).
"The cause of the incident is unknown at this time and will be investigated," Central Command said.
Who are these Iraqi irregulars? Ba'athists? Shi'ites? Disgruntled soldiers?