The AN/ALQ-99 is a U.S. Navy airborne electronic warfare jamming pod carried on aircraft like the EA-18G Growler. It is designed to detect, analyze, and actively jam enemy radar and communications systems, primarily to suppress integrated air defenses and protect aircraft. 

Each pod is a self-contained jammer, using onboard receivers and processors to identify hostile emitters and then transmit powerful interference signals to degrade or deny their operation. The pods are externally mounted and powered by a ram air turbine, allowing them to generate significant jamming power independently of the aircraft.

In practice, multiple ALQ-99 pods can be carried simultaneously, covering different frequency bands to provide wide-spectrum electronic attack, ranging from radar disruption to communications denial.

On display at the Marine Corp Museum - come check it out!