Shares of United Continental (UAL) - Get Report are up Wednesday after PAR Capital Management and Altimeter Capital Management raised their stakes in the airline.

Analysts at UBS also upgraded American Airlines (AAL) - Get Report , which is merging with United, to buy from hold, noted TheStreet's Jim Cramer, co-manager of the Action Alerts PLUS portfolio, on CNBC's "Mad Dash" segment. 

American Airlines trades at just 8 times earnings, generates a lot of cash flow, is buying back stock, and, like every other airline, is seeing its largest raw input cost -- fuel -- continue to move lower, Cramer said. 

So all of that would lead to an appreciating stock price, right? Well, not quite. Although it doesn't make sense, airline stocks continue to get pushed lower as the price of crude oil continues lower, he said. 

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LUV, UAL and AAL data by YCharts

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This makes no sense, he added. Investors apparently think the drop in oil prices means a drop in demand rather than robust supply, and assume a lower demand for travel, Cramer said. 

Southwest Airlines (LUV) - Get Report is a good example. The company reported a great quarter, has almost no international exposure and isn't cutting fare prices. Revenue have climbed while input costs are falling, yet the stock is down 11.5% on the year. 

Lower oil is "so fabulous" for the airlines, but investors aren't recognizing that. Cramer drew a broader market conclusion that stocks will likely remain under pressure until the "hatred" for well-managed, strong companies "decouples" from commodities and the stock prices stop declining simply because oil prices are declining.

At the time of publication, Cramer's Action Alerts PLUS had no position in companies mentioned.