Four CH-47 Chinooks can carry dozens of people on stretchers, or haul enormous loads of equipment or supplies. Two smaller UH-60 Black Hawks serve as workhorse transport helicopters.
The helicopters were supposed to arrive Tuesday but were delayed by bad weather. The Pentagon says they will fly when the weather clears. The helicopters will be flown by U.S. crews at the discretion of the Pakistani military. Pakistan publicly resists any U.S. military presence inside the country, but has accepted humanitarian help before.