This year is on course to be the safest ever for commercial aviation, with roughly one passenger death for every 7.1 million air travelers worldwide, although aviation officials warn that improving accident statistics mask lingering dangers.

With only days left, 2011 appears set to eclipse the postwar record low rate of passenger fatalities, set in 2004 at one per 6.4 million passengers, according to Ascend, a consulting firm in London. This year also appears set to end with among the lowest total number of passenger deaths,...