** Shares of major North American airline carriers fall in premarket trading after Jefferies downgrade ** Southwest Airlines LUV.N leading losses with 2.7% decline, while Delta Air Lines DAL.N is down 1.42%; American Airlines AAL.O down 1.71% and United Airlines UAL.O falls 1.30%

** Jefferies downgrades AAL and DAL to "hold" from "buy", while cuts LUV to "underperform" from "hold"

** Brokerage says corporate and consumer sentiment to remain soft due to macro uncertainty ** Brokerage also downgrades Air Canada AC.TO to "underperform" from "hold"

(Reporting by Rashika Singh in Bengaluru)

((Rashika.singh@thomsonreuters.com))