Wall Street analysts are really warming up to legacy carrier United Continental Holdings Inc (UAL -2.52%). On Tuesday, the company received its second analyst upgrade in as many weeks as the research team at UBS (NYSE: UBS) put a buy rating on United.

Analysts' growing bullishness seems to be driven by the belief that competitive pressure is easing for United, which will allow the company to post better unit revenue results going forward. This may be true in the short-term, although even that is unclear.

However, in the long run, United is likely to face more competition -- not less. United is a big player in many of the top U.S. markets, and its high costs -- even compared to legacy peers Delta Air Lines (DAL -2.62%) and American Airlines (AAL -2.18%) -- make it an obvious target for up-and-coming rivals.

Lower competitive pressure?
Last week, analysts at Raymond James (NYSE: RJF) boosted their rating on United Continental to outperform. The analysts argued that, in addition to benefiting from improving industry demand trends, United will also see "easing competitive pressure in its hubs."

Analysts are looking for United to post better unit revenue results starting this quarter

The UBS upgrade had a similar rationale. The analysts stated that data from their proprietary fare tracker and a study of competitors' capacity plans on United routes showed that unit revenue will accelerate in Q2.

There are definitely a few key markets where competitive pressure is easing. For example, United and Delta are both decreasing their Japan operations in response to the yen's devaluation. Delta recently ended its flight to Tokyo from United's San Francisco hub, while United dropped service to Tokyo from Delta's Seattle gateway. JetBlue Airways (JBLU -3.12%) is also dropping a few markets where it competes with United to free up capacity for its expansion at Washington's Reagan Airport.

The other side of the coin
Still, it's not like competitors are afraid of challenging United. On the lucrative transcontinental routes from New York to Los Angeles and San Francisco, American Airlines and JetBlue are stepping up their games in a big way. American and JetBlue are deploying brand new Airbus A321s on the routes, and both carriers are outfitting them with flat-bed premium cabins to match United, while running more frequencies.

JetBlue is putting flat-bed seats on some transcontinental flights this year (Photo: JetBlue)

United's dominance in the Pacific region outside of Japan has also come under fire. Competitive capacity increases last year caused United's unit revenue in the Pacific region to drop. The trend of rapid capacity growth between the U.S. and Asia shows no signs of reversing.

Cathay Pacific began flying between Newark and Hong Kong last month, giving United its first competition on that route. Cathay also plans to boost service to Chicago and Los Angeles later this year. Air China will start competing with United on the Beijing-Washington route in a few months. Meanwhile, in June, Delta will launch nonstops from Seattle to Seoul and Hong Kong, while American will begin nonstops from Dallas/Fort Worth to Shanghai and Hong Kong.

More competition will come
To the extent that United is facing less competitive pressure this year than in previous years, it can thank Virgin America and Spirit Airlines (NASDAQ: SAVE). Both of these smaller carriers have been growing very rapidly, but they are taking a bit of a breather in 2014. However, it will be a brief respite.

Ultimately, Spirit's rapid growth could put pressure on the legacy carriers (Photo: Spirit Airlines)

Spirit plans to grow capacity by 16.7% this year (which is low for Spirit), but the company will make up for this by growing nearly 30% in 2015. Virgin America's growth came to a complete halt last year, but the company will start increasing its aircraft fleet again in the second half of 2015. Virgin America's two main bases (San Francisco and Los Angeles) are also United hubs, so Virgin's growth has a particularly strong impact on United.

United's high cost structure makes it a target for competitors. Last year, United's consolidated unit cost excluding fuel, special items, and third-party business expenses totaled $0.0966. At Delta, the comparable figure was $0.0950, and at American it was $0.0935.

While United is within a few percentage points of the other legacy carriers, that can be the difference between a profit and a loss in the notoriously low-margin airline business. United needs to charge higher fares to earn a solid profit, and this gives potential competitors an opportunity to undercut it on price.

Foolish final thoughts
Analysts are looking for unit revenue acceleration at United Continental this quarter. In a literal sense, this should be very easy: Because United is expected to report a unit revenue decline for Q1, even a return to breakeven would be "acceleration" in some sense.

Of course, United will do better than that. Even so, assuming United does post a unit revenue decline for Q1, the carrier will be hard-pressed just to match last year's 3.2% unit revenue gain for the full year. If United has anything going for it in 2014, it is cost containment, not accelerating unit revenue.

Thus, I'm still expecting United Continental to underperform the rest of the airline industry this year, just as it did last year. If United does manage to beat last year's 3.2% unit revenue growth in 2014, that would be a buy signal. However, right now, the bull case for United is based on hope more than facts.