Iran shooting down two American military aircraft marks an exceedingly rare assault for the U.S. that has not happened in more than 20 years.

The downing of American fighter jets in the skies over Iran this week marks the first time in decades that the United States lost a military warplane to enemy fire, according to a retired Air Force general.

These bases host the largest aircraft fleets in the country, from fighter training hubs to testing centers and massive operational air wings.

Search and rescue is underway after the first US combat aircraft loss over Iran, reports say. This isn't the first aircraft lost in the war though.