Southwest Airlines Co (NYSE: LUV) early Friday [Mar 10, 2017 | 6:37am] cut its outlook for a key industry metric amid its monthly update, sending its shares lower in premarket trading.

The Dallas-based airline operator first noted that airline passenger miles rose 1.1% to 8.7 billion for the month of February. Capacity also gained 1.2%, to 11.0 billion available seat miles during the month.

Load factor was flat for February at 79.0%, while year-to-date load factor is down 60 basis points to 77.6%.

Based on the trends above, LUV now expects its Q1 operating revenue per ASM (RASM) to fall in the 2% to 3% range, compared with year-ago levels. It had previously called for a 1% RASM drop.

The company blamed higher completion rates and weather-related traffic issues for the sluggish outlook:

A better-than-expected February trip completion rate and the loss of traffic from the heavy rainfall in California are contributing factors to this revised RASM outlook. In addition, there was unexpected softness in close-in demand in the second half of February that has since rebounded in March. Bookings and unit revenue trends beyond first quarter 2017 remain encouraging.

Southwest Airlines Co shares fell $0.91 (-1.61%) in premarket trading Friday. Year-to-date, LUV had gained 13.08% prior to today’s news, versus a 5.96% rise in the benchmark S&P 500 index during the same period.

LUV currently has a StockNews.com POWR Rating of A (Strong Buy), and is ranked #1 of 18 stocks in the Airlines category.