(Reuters) – Shares of United Continental Holdings (UAL.N) rose as much as 12 percent on Thursday to their highest level since late 2007, a day after the airline said a key revenue measure improved in December.

The Chicago-based owner of United Airlines said on Wednesday its unit revenue, known as passenger revenue per available seat mile, rose as much as 12.5 percent in December compared with a year earlier as the airline benefited from a late Thanksgiving holiday and a stormy winter.

United also attributed part of the gain to some 1200 flights it canceled because of winter storms.

A late Thanksgiving helped other airlines in December. Southwest Airlines Co (LUV.N) said Wednesday unit revenue rose between 14 percent and 15 percent from the same month in 2012. Delta Air Lines Inc (DAL.N) said Monday unit revenue rose 10 percent.

United said consolidated traffic grew 4.1 percent in December and unit revenue grew 11.5 percent to 12.5 percent, more than United had originally expected.

Some analysts thought United’s strong December performance would continue into 2014 and translate into a possible announcement about returning capital to shareholders.

Analyst Helane Becker of Cowen raised her earnings estimates for the company given December traffic results and now expects United to earn $2.86 in the fiscal 2013, up from a prior estimate of $2.09.

Wall Street analysts, on average, expect the company to earn $1.61 cents, as per Thomson Reuters I/B/E/S. United is expected to post results this month.

Shares of the company were trading up 9.22 percent late Thursday morning on the New York Stock Exchange. They touched a high of $46.19 earlier in the day.

(Reporting by Nivedita Bhattacharjee in Chicago; Editing by Meredith Mazzilli)