Grieving relatives continued to pray for the safety of those in an Indonesian plane missing since New Year's Day as rescuers continued their search in the treacherous mountains in southern Sulawesi. The relatives streamed into a church near the Hasanuddin Airport in Makassar as missionaries comforted them and led them to prayers for the missing airliner a week after it vanished in bad weather with 102 aboard. "We came here to visit and give them faith and strength for this disaster that they are facing," missionary Rin Wowiling Watung told Reuters late on Sunday (Jan 7). Meanwhile, soldiers trudged through the mountainous regions of Tana Toraja in southern Sulawesi over the weekend in search of the missing airliner. The area is rocky with treacherous gullies making the search more arduous for the rescuers. Officials also said two Indonesian Air Force helicopters joined the search on Monday (Jan 8) to locate the missing airliner, focussing on the Bone Strait between the two southern arms of Sulawesi island and the onshore areas of western Sulawesi, A U.S. ship with sonar capability and the ability to detect underwater metal, USNS Mary Sears, will arrive on Tuesday (Jan 9) to join the search, which already includes planes, helicopters, navy ships, and thousands of troops and police on the ground. The search for the 17-year-old Boeing 737-400 operated by Indonesian budget airline Adam Air has been hampered by rain, clouds and wind, with the area's jungle-covered mountainous terrain also making it difficult to spot things from the air. The region also lacks roads to reach areas on the ground and communications infrastructure is often poor. The plane disappeared less than three days after a ferry capsized and sank off Java. Indonesian President Susilo Bambang Yudhoyono has called for investigations into what went wrong in both cases as well as a general probe into the state of Indonesia's transport system. The network serves 220 million people on an archipelago of 17,000 islands which stretches as wide as the United States.