An analyst downgrade was the news that pushed down the share price of Sabre (SABR -3.43%) on the second business day of the week. The travel industry software mainstay lost altitude to the tune of over 3%, on a day when the S&P 500 (^GSPC 0.40%) index ended up posting an increase of 0.4%.A switch to sellWell before market open, Bernstein SocGen prognosticator Alex Irving made that Sabre recommendation change. For him, the travel software specialist is now an underperform (sell, in other words), where former ...