* Air Canada posts record 82.1 pct Dec. load factor * No. 2 carrier WestJet records record 81.9 pct * Regional airline Porter inches higher to 64.3 pct * All three carriers report 2012 gains, Porter alone sees Q4 drop TORONTO, Jan 7 (Reuters) - Canada's airlines flew fuller planes in December, with dominant carrier Air Canada and No. 2 rival WestJet Airlines reporting record monthly passenger levels on Monday. Air Canada shares rose 5 percent after reporting that its load factor, or the percentage of available seats filled with paying customers, rose to 82.1 percent in December from 81 percent a year earlier. The airline, which is preparing to launch a low cost vacation carrier this summer, said traffic increased by 3.2 percent in December as capacity, measured by available seat miles, rose 1.8 percent. "The record December results highlight that overall air travel demand remains healthy across the geographic segments," said National Bank Financial analyst Cameron Doerksen in a note. The analyst, who said Air Canada's fourth-quarter load factor bettered his forecast 79.5 percent, was reviewing his forecast. Air Canada said its fourth-quarter load factor climbed 2.3 percentage points to 81.2 percent, while the full-year figure rose 1.1 percentage points to a record 82.7 percent. Calgary-based WestJet said it reached a record December load factor of 81.9 percent, up from 80.9 percent in the same period last year, as traffic increased 7.2 percent and capacity grew 6 percent. The airline's fourth-quarter load factor increased 3.2 percentage points to 81.9 percent, while its 2012 load rose to 82.8 percent from 79.7 percent in 2011. Chief Executive Gregg Saretsky said December's load factor was the sixth consecutive monthly record and that forward bookings remain strong. WestJet is scheduled to take delivery of its first two Q400 turboprop planes in June for the launch of its new regional airline, WestJet Encore. The new carrier, which will heat up competition with Air Canada and smaller Porter Airlines, will announce its schedule in February. Porter said its December load factor edged slightly higher to 64.3 percent from 63.9 percent in the same period last year, as traffic grew 3.5 percent and capacity increased 2.9 percent. Privately-held Porter, which has expanded rapidly since its launch in 2006, said its fourth-quarter load factor fell to 59.3 percent from 65.9 percent. The airline's 2012 load factor nudged up to 62 percent from 61.7 percent. Air Canada shares rose 5 percent, or 9 Canadian cents, to C$1.86 in early trade on the Toronto Stock Exchange. WestJet shares fell 3 Canadian cents to C$20.18.