UPDATE 3-WestJet says weak Alberta economy weighing on demand
* Q1 revenue/available seat mile to fall 10-12 pct
* Cuts 2016 system-wide capacity forecast
* Q4 earnings/shr C$0.51 vs analyst estimate C$0.63
* Shares fall to more than 3-yr low (Adds details from conference call)
By Anet Josline Pinto
Feb 2 (Reuters) - WestJet Airlines Ltd's quarterly revenue per available seat mile, a key measure of profitability, is poised for its steepest decline since 2009, as Alberta's weakening economy weighs on leisure and business travel from the western Canadian province.
The company's shares fell as much as 11.5 percent to a more than three-year low of C$16.55.
Alberta, known for its oil-rich resources, has been hit by a near 70 percent plunge in oil prices since June 2014.
Airlines in western Canada that were once blooming in the oil-rich region have been recording a significant decline in passenger traffic to and from and within Alberta. Continued...