A gauge of U.S. airlines' revenue performance edged higher in November, but analysts warned that revenue could face renewed pressure in the slower winter travel season.

Continental Airlines Inc. this week estimated that mainline unit revenue, or revenue per available seat mile (search) (RASM), was flat to up 1.0 percent in November compared with a year earlier, but weaker than the carrier's revenue estimates for the previous month.

In early November, Continental (CAL) had predicted its October mainline unit revenue rose between 0.5 percent and 1.5 percent.

Analysts use Continental's unit revenue figures as a gauge of industry health because it is the only carrier that releases its revenue estimates each month. In recent months, however, the airline's estimates have come in stronger than industry RASM.

"Going forward, we may see revenues continue to come under pressure as we have now entered the seasonally more difficult period of the year," wrote Credit Suisse First Boston analyst Jim Higgins in a research note.

Data on industry-wide unit revenue from the Air Transport Association (search), an industry trade group, are due later this month.

Systemwide unit revenue declined 2.9 percent in October from a year earlier, according to Wall Street analysts who receive the data.

Airlines that have released November traffic figures so far have reported gains. AMR Corp. (AMR), parent of American Airlines, said traffic increased 8.2 percent, while capacity, or available seat miles, increased 4.1 percent.

Southwest Airlines (LUV) said its traffic increased 14.1 percent in November on a 11.1 percent capacity increase.

Continental said its traffic increased 11.2 percent in November on a 7.9 percent increase in Capacity.

Many airlines cited soaring oil prices as a leading contributor to losses in the third quarter. But airline stocks gained earlier this week as oil prices declined. U.S. crude oil futures, which touched a record high of $55.67 a barrel on Oct. 25, traded near $43.30 a barrel on Friday after a steep slide on Wednesday and Thursday.

Airline stocks retraced some of those gains on Friday as oil prices stabilized. Shares of AMR Corp. were down 28 cents, or 2.6 percent, at $10.35, while Southwest shares fell 4 cents to $16.26, both on the New York Stock Exchange.

Shares of Continental slipped 30 cents, or 2.4 percent, to $12.23, also on the NYSE.