** Shares of major U.S. airlines fall in early trading on worries around a slowdown in discretionary spending amid a tariff war

** U.S. President Donald Trump's new 25% tariffs on imports from Mexico and Canada take effect on Tuesday, along with doubling of duties on Chinese goods to 20%

** Delta Air Lines DAL.N down 6.9%, United Airlines UAL.O down 8% and American Airlines AAL.O down 6%

** Budget carriers Southwest Airlines LUV.N down 3.2% and JetBlue Airways JBLU.O down 8.5%

** "As retailers and other businesses warn their customers about higher prices from tariffs, there's a feeling that people will have less discretionary spending available for holidays and vacations," says Michael Ashley Schulman, partner and chief investment officer at Running Point Capital

** "Businesses may also reduce corporate travel in order to help keep their expenses in check and maintain margins," Schulman says

** YTD, S&P 1500 airlines sub-index .SPCOMAIR down 6.3%

(Reporting by Shivansh Tiwary in Bengaluru)

((Shivansh.Tiwary@thomsonreuters.com; +91 9708363192; X: @Shivansh_19_;))