not to convert their fleets to natural gas. Further, the criteria pollutant (such as Oxides of Nitrogen (NOx)) reduction benefits of natural gas engines may degrade over time. The success of our business strategies and initiatives depends on sufficient availability and adoption of high-performing natural gas vehicles, and as a result, any production delays or failures by the third-party manufacturers of these vehicles or their engines could harm our results of operations, business and prospects.
If there are improvements in or perceived advantages of non-natural gas vehicle fuels or engines powered by these fuels, demand for natural gas vehicles may decline.
Use of electric heavy-duty trucks, buses and refuse trucks, which are key customer markets for our business, or the perception that electric vehicles providing satisfactory performance at an acceptable cost may soon be widely available for these or other applications, could reduce demand for natural gas vehicles generally and in these key markets. In addition, hydrogen, renewable diesel and other alternative fuels in development may prove to be, or may be perceived to be, cleaner, more cost-effective, more readily available or otherwise more beneficial alternatives to gasoline and diesel than conventional or renewable natural gas. Further, technological advances in the production, delivery and use of gasoline, diesel or other alternative vehicle fuels, or the failure of natural gas vehicle fuel technology to advance at an equal pace, could slow or limit adoption of natural gas vehicles. For example, advances in gasoline and diesel engine technology, including efficiency improvements and further development of hybrid engines, may offer a more cost-effective way for operators to use a cleaner vehicle fuel, which could reduce the likelihood that fleet customers purchase natural gas vehicles or convert their existing vehicles to natural gas. If any of these risks occur, our industry, prospects and results could materially suffer.
We have a history of losses and may incur additional losses in the future.
We incurred pre-tax losses in 2017, 2018 and the nine months ended September 30, 2020. During 2018, 2019 and the nine months ended September 30, 2020, our results were positively affected by $26.7 million, $47.1 million, and $14.8 million of AFTC revenue, respectively. We may incur losses in future periods and we may never sustain profitability, either of which would adversely affect our business, prospects and financial condition and may cause the price of our common stock to fall. Furthermore, historical losses may not be indicative of future losses due to the unpredictability of the COVID-19 pandemic, and our future losses may be greater than our past losses. In addition, to try to achieve or sustain profitability, we may choose or be forced to take actions that result in material costs or material asset or goodwill impairments. For instance, in the third and fourth quarters of 2017, we recorded significant charges in connection with our former natural gas fueling compressor manufacturing business (which we combined with another company’s natural gas fueling compressor manufacturing business in the CEC Combination), our closure of certain fueling stations, our determination that certain assets were impaired as a result of the foregoing, and other actions. We review our assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset or asset group may not be recoverable and we perform a goodwill impairment test on an annual basis and between annual tests in certain circumstances, in each case in accordance with applicable accounting guidance and as described in the financial statements and related notes included in this report and our 2019 Form 10-K. Changes to the use of our assets, divestitures, changes to the structure of our business, significant negative industry or economic trends, disruptions to our operations, inability to effectively integrate any acquired businesses, further market capitalization declines, or other similar actions or conditions could result in additional asset impairment or goodwill impairment charges or other adverse consequences, any of which could have material negative effects on our financial condition, our results of operations and the trading price of our common stock.
Increases, decreases and general volatility in oil, gasoline, diesel and natural gas prices could adversely affect our business.
The prices of natural gas, crude oil, gasoline and diesel can be volatile and this volatility may continue to increase. Factors that may cause volatility in the prices of natural gas, crude oil, gasoline and diesel include, among others, changes in supply and availability of crude oil and natural gas, government regulations, inventory levels, consumer demand, price and availability of alternatives, weather conditions, negative publicity about crude oil or natural gas drilling, production or importing techniques and methods, economic, health and political conditions, transportation costs and the price of foreign imports. Specifically, prices for crude oil, which is the commodity used to make gasoline and diesel, have been