Shares of Delta lose altitude after airline reports a drop in key December revenue figure

Delta Air Lines Inc. said Monday that a key revenue figure fell 4.5 percent in December, which it blamed on holiday travel that spilled over into other months because of the changing calendar.

The revenue figure fell about 1 percent for the entire fourth quarter, Delta estimated.

Shares of Delta dropped 82 cents, or 1.7 percent, to close at $48.36 on Monday. They rose 79 percent in 2014.

Delta said that revenue for every seat flown one mile fell in December partly because some Thanksgiving and Christmas travel occurred in other months. The Sunday after Thanksgiving, one of the busiest travel days of the year, was in November after being pushed into December in 2013.

The Atlanta-based airline said that December traffic rose 2.1 percent, as passengers flew 16.12 billion miles. U.S. traffic rose faster than international.

Delta added 4 percent in passenger-carrying capacity, and the average flight was 83.7 percent full, down from 85.2 percent a year earlier. All the figures include Delta Connection regional flights.