Hit by winter storms, cancellations and labor costs, Pinnacle Airlines (PNCL) said on Thursday that it swung to a loss in the fourth quarter over a year ago profit, sending its shares tumbling.

The Memphis-based company posted a net loss of $4.2 million, or 23 cents a share, compared with a profit of $5.6 million, or 31 cents a share, in the same quarter last year.

Earnings were negatively impacted by costs related to the inclusion of six Q400 aircraft to Pinnacle subsidiary Colgan Air's fleet. The company’s workforce jumped 17% on the new fleet, lifting labor and training expenses. 

Financial results were also impacted by winter storms in December, which led to a higher percentage of cancelled flights during the period.

Excluding these one-time charges and others related to a $10.9 million signing bonus and payroll taxes, the company earned 14 cents a share, narrowly below average analyst estimates polled by Thomson Reuters of 17 cents.

"We had a challenging fourth quarter," Pinnacle CEO Philip Trenary said in a statement.

Revenue for the independent regional airline was $291.6 million, up from $209.2 million a year ago, missing the Street’s view of $296.84 million.

Follow Jennifer Booton on Twitter at @Jbooton