The U.S. military will double its aid drop-offs to isolated survivors along Sumatra island's devastated coast by Friday with the arrival of more helicopters, officials said Thursday. The ability to treat survivors also has been strengthened, but no one should think that the worst is over yet, said Pierre King, operations officer for the International Organization for Migration, adding that there are critical medical needs to deal with once the immediate emergency eases. "We're still in the emergency period," said King, from France. "But we should start thinking about the transition. The whole medical system is in shambles. We have to avoid doctors saying, `OK there's no more suffering, let's go.' The Banda Aceh airport was a beehive of activity, with helicopters and aid flights landing and taking off. Supplies were being unloaded from a British Royal Air Force C-130 to be shuttled out by chopper. U.S. Marine Col. Dave Kelley, chief of U.S. Support Group-Indonesia, based at the airport, said he is trying to boost the facility's capacity for handling so much aid and was searching for other landing fields. With vessels arriving from a U.S. Marine strike group either late Thursday or Friday to join the carrier group headed by the USS Abraham Lincoln, the number of operational helicopters should double from about 10 _ which flew 45 missions on Wednesday _ to 20.