The grounding of Boeing Co.’s BA, -0.67% 737 Max jets by the U.S. and Canada on Wednesday, and by many other countries earlier this week, is “not…a major factor” for the airlines it rates, S&P Global Ratings said Thursday. The groundings came after there was a deadly crash of a 737 Max jet over the weekend, a second in less than 6 months. Among the air carriers with the most exposure to the 737 Max family of jets, shares of Southwest Airlines Co. LUV, +0.65% rose 0.8% in afternoon trade Thursday, but have lost 1.5% this week; American Airlines Group Inc. AAL, +0.38% tacked on 0.2% on the day and were little changed on the week; and United Continental Holdings Inc. UAL, +0.20% edged up 0.1% on the day but have lost 1.3% this week. In comparison, the NYSE Arca Airline Index XAL, -0.43% has tacked on 2.0% this week and the S&P 500 SPX, -0.13% has gained 2.4%. “We could revise our assessment of the 737 MAX aircraft if we conclude that the recent accidents will lead to a lasting diminution of collateral value or resale liquidity, but that would not become clear for some time,” S&P Global said.

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