Since our incorporation in 1949, our primary business has been the safe and reliable transportation of personnel to, from, and among offshore platforms for customers engaged in the oil and gas exploration, development, and production industry. Although in recent years we have entered several new domestic and international markets, a large portion of our offshore flight operations continues to be concentrated in the Gulf of Mexico, where we are a leading provider of such services. Since late 1997, we have also provided air medical transportation for hospitals and for emergency service agencies where we operate principally as an independent provider of medical services. In addition, we perform helicopter maintenance and repair services, primarily to existing customers that own their own aircraft. At December 31, 2018, we owned or operated 239 aircraft domestically and internationally, 125 of which were dedicated to our Oil and Gas segment, 108 of which were dedicated to our Air Medical segment, and 6 of which were dedicated to other operations.
Operating Revenues - Operating revenues for the year ended December 31, 2018 were $674.4 million, compared to $579.5 million for the year ended December 31, 2017, an increase of $94.9 million, or 16.4%. Oil and Gas segment operating revenues increased $81.8 million for the year ended December 31, 2018. As discussed further below, this increase is attributable principally to revenue derived from our recently-acquired HNZ Offshore Business and secondarily from an increase in revenues from our legacy international Oil and Gas operations, partially offset by a decrease in revenues from our Gulf of Mexico operations. Operating revenues in our Air Medical segment decreased $0.1 million due principally to decreased revenues attributable to our independent provider operations. Technical Services operating revenues increased $13.2 million due to an increase in services provided to our government customer under projects discussed further below.