WestJet Airlines Ltd, Canada's No. 2 airline, said on Monday its flights in November were not as full as a year earlier and warned delayed holiday bookings would hold back a revenue benchmark in the current quarter.

In contrast, No. 1 Air Canada and upstart Porter Airlines filled more available seats than in November 2010.

WestJet expects fourth-quarter revenue per available seat mile, used to compare revenue performance among airlines, to grow 4 to 5 percent. It had previously forecast growth in line with last quarter's 5.8 percent gain.

We are noticing a slight shift in booking patterns this holiday season with more travel spilling into January as school breaks are starting later in December, said Chief Executive Gregg Saretsky in a release.

Its load factor - the percentage of available seats filled with paying customers - fell to 77.6 percent last month, from 77.7 percent in November last year, as growth in capacity slightly outpaced traffic.

WestJet's available seat miles, or capacity, rose 4.5 percent over last year, while traffic rose 4.4 percent.

Air Canada, Canada's biggest airline, said its load factor rose to 75.9 percent from 74.8 percent, as capacity rose 1.4 percent and traffic rose 3.0 percent.

Closely held competitor Porter Airlines said its November load factor rose to 65.9 percent, from 54.0 percent last year, as capacity rose 20.7 percent and traffic jumped 47.3 percent.

Shares of WestJet closed down 1.4 percent at C$11.28 on Monday afternoon on the Toronto Stock Exchange, and Air Canada closed down 1.8 percent at C$1.08.