Almost two weeks after Hurricane Maria hit Puerto Rico, authorities still have problems distributing supplies.
Mayors from several Puerto Rican cities, including San Juan, have criticized the federal response to the natural disaster.
But Federal Emergency Management Agency Administrator Brock Long defended the relief effort Sunday — calling it the "most logistically challenging event that the United States has ever seen."
Downed trees, mudslides and flooding have hindered efforts to move supplies by truck. Roughly a week after Maria hit, at least 12 sections of highways around the island were inaccessible.
An Army general working with FEMA says they've relied on air deliveries for some of the areas that are hardest to reach.
Air drops aren't a one-size-fits-all solution, though. Another relief leader noted Puerto Rico's mountainous terrain can make air deliveries dangerous for both crews and those on the ground.
Fuel and communications have also been big obstacles.
But those generators run on gas, and gas shortages are also plaguing the island.
Downed cellphone sites have even made it hard for officials to communicate with drivers transporting aid.
However, some hammered Long for his comment about the relief effort being the "most logistically challenging event" in U.S. history.
Critics on social media argued events like moon landings, the Normandy invasion and the Berlin airlift have had more challenging logistics.