By Abhijith Ganapavaram and Kannaki Deka (Reuters) -Southwest Airlines Co said on Friday it expects to post a loss in the fourth quarter after it canceled over 16,700 flights between Christmas and New Year’s Eve due to a tech meltdown. The mass cancellations during the peak season for U.S. airlines will result in a pre-tax hit of $725 million to $825 million to quarterly earnings, said Southwest, which had earlier forecast a strong profit. Shares of the company fell 2.8% premarket before turning positive in morning trade. On Thursday, the largest U.S. domestic airline promised a thorough revie…