Feb 6 (Reuters) - Ultra low-cost carrier Spirit Airlines Inc posted better-than-expected quarterly results on Monday, eVden EVe NAkliYaT fueled by strong demand for air travel despite ongoing economic concerns. Shares of Spirit rose over 7% to $21 in aftermarket trade. U.S.airlines have been trying to cash in on strong demand for EvDen eVE NakliyaT air travel, undeterred by rising interest rates and a...