BANGOR, Maine — More grim passenger statistics were released this week from Bangor International Airport, prompting fresh concerns that airlines unable to fill planes flying out of the city might be forced to leave altogether.

Risteen Masters, BIA’s marketing manager, presented members of the city’s transportation and infrastructure committee on Tuesday with statistics for January 2009. The numbers show an overall decrease in passenger traffic of 12.4 percent from 2008 and a load factor of 66 percent, which is 5 percent lower than a year ago.

Load factor is essentially a measure of how full a plane is. If passenger load factors decrease substantially, carriers often must consider whether those flights should be eliminated. Masters said the continued downtown in the airline industry could prompt airlines to make capacity adjustments.

Two airlines that serve BIA, Allegiant Air and Continental Airlines, actually posted positive increases in passengers for January 2009 of 9 percent and 44 percent, respectively. Two others, Delta Air Lines and US Airways, saw decreases of about 25 percent each. Because those two carriers account for the largest market share at BIA, the entire airport’s numbers remain down.

Additionally, Continental’s increase of 44 percent is misleading. The carrier added a daily flight recently, but the load factor for Continental is only 50 percent, which means those flights are about half full. By comparison, Allegiant also recently added a flight, but that carrier has posted a load factor of 92 percent.

Masters also advised city councilors Tuesday that there have been growing signs of rising oil prices that would almost certainly affect the airline industry.

Since peaking in November 2005, BIA has seen its passenger statistics drop steadily to their lowest point in more than eight years.

BIA is not alone, though. Other regional airports have seen declining numbers recently as well. In Portland, traffic was down 6.4 percent in January, while Manchester, N.H., saw a decrease of 9.3 percent in December, the most recent data available.