3 U.S. MQ-9 Reaper drones, worth about $30 million each, have crashed off Yemen since November

A U.S. MQ-9 Reaper drone crashed off the coast of Yemen this week, possibly downed by Houthi rebels, according to a U.S. official. The cause is under investigation.

The Iran-backed Houthis have brought down two other MQ-9s since November, the first in early November and then another in February. Each drone costs roughly $30 million, according to the Congressional Research Service. 

The drones flying off the coast of Yemen are part of the U.S. military's efforts to help defend commercial and military ships against ongoing attacks by the Houthis.