Delta's auditor raises doubt about airline's future (DAL) By Matt Andrejczak SAN FRANCISCO (CBS.MW) -- Delta Air Lines (DAL) auditor raised doubts Wednesday about the future of the nation's third largest carrier. Delta's recurring losses and liquidity issues "raise substantial doubt about the company's ability to continue as a going concern," Deloitte & Touche LLP said in a regulatory filing. Shares of Delta closed at $4.10, up 1 cent