The US president made an official visit to shore up ties before heading to Japan for his last G7 summit.
Tests found high lead content in two more batches of green tea and energy drink products.
The deal, signed during US President Barack Obama's visit to Vietnam, represents a coup for Boeing.
Da Nang, Khanh Hoa and Phu Quoc have seen sharp increases in the number of tourist arrivals.
Dinh Cong Tuong is proud of his collection that he says can showcase a part of Vietnam's rich culture.
Buses will traverse downtown and Chinatown from morning to night.