It has undermined peace and stability in the East Sea, eroded bilateral political trust and negatively impacted the neighbourliness and sentiments between the two peoples, he added. 
The spokesperson stated that Vietnam asks China to immediately end, not to repeat such an action and take practical and specific acts to contribute to maintaining peace, stability, security, maritime and aviation safety and freedom in the East Sea. 
The Vietnamese foreign ministry said that China's pilot flight to an airport built illegally on a reef in Truong Sa (Spratly) archipelago in the East Sea "seriously violated Vietnam's sovereignty". 
The flight to Chu Thap (Fiery Cross) reef "went counter to the common perception of the two countries’ leaders, the agreement on basic principles guiding the settlement of Vietnam – China issues at sea and the spirit of the 2012 Declaration on the Conduct of Parties in the East Sea," the ministry spokesman said. He was using the Vietnamese name of the sea otherwise known as South China Sea.
China's action undermined peace and stability in the East Sea, eroded bilateral political trust and negatively impacted the neighborliness and sentiments between the two peoples, Binh said. He said that Vietnam demands that China immediately end and not repeat such an action and take practical and specific acts to contribute to maintaining peace, stability, security, maritime and aviation safety and freedom in the East Sea. 
It also affects peace and stability in the East Sea, compromising the political trust between Vietnam and China and negatively impacting the neighborly relations, Binh said.
“Vietnam resolutely opposes China’s action and demands that Beijing stop it and not repeat any similar move, as well as apply practical and specific measures to contribute to the maintenance of peace, stability, security, safety, and freedom of navigation and aviation in the sea area,” the spokesperson stressed.
The same day, a representative from the Vietnamese Foreign Ministry presented a diplomatic note to Chinese embassy counterpart  in Hanoi opposing China’s action.