Southwest Airlines Co. LUV shares fell by 1.3% Thursday in premarket trading after the company announced first-quarter earnings that were below Wall Street expectations. The carrier reported a loss of $159m, or a loss per share of 27c, compared to a loss per share of 32c in the previous year’s quarter. FactSet surveyed analysts who expected a loss per share of 23 cents. Southwest’s revenue increased 21.6% over the past year to $5.71 Billion, but fell short of FactSet’s consensus estimate of $5.73 Billion. The company claimed that it had a negative impact on its finances.