U.S. airlines spent $6.5 billion on airplane fuel in April, another sign of the economic damage wrought by the U.S.-Israeli war with Iran.

The total is over double what airlines reported paying back in February. The Department of Transportation reported that airlines collectively paid $3.23 billion in February, while in March they paid $5.06 billion. The newest fuel costs came from the International Air Transport Association, causing it to revise its industry projections.