Boeing landed a $7.8 billion deal with Vietnam Airlines, the White House announced as President Joe Biden's visited with Prime Minister Pham Minh Chinh in Hanoi. Boeing stock slid early Monday after edging higher premarket. X Vietnam Airlines will purchase 50 of the Boeing (BA) 737 Max jets, President Biden said during a roundtable with Vietnamese officials and executives from the aviation, semiconductor and tech sectors. Vietnam Airlines currently has a fleet of 100 aircraft, including 15 Boeing 787 Dreamliners. The new jets will replace planes more than a decade old, Barron's reported citing Vietnam state media. Meanwhile, the deal…