March 10 (Reuters) - Southwest Airlines Co cut its forecast for a key revenue measure on Friday, citing "unexpected softness" in demand for last-minute flight bookings in the second half of February.
The No. 4 airline by passenger traffic said it expects first-quarter operating unit revenue to fall in the 2-3 percent range, compared with its previous forecast of flat to down 1 percent.
Unit revenue compares sales to the number of seats an airline flies and how far it flies them. (Reporting by Ankit Ajmera in Bengaluru; Editing by Saumyadeb Chakrabarty)