Earlier this year, struggling jet maker Bombardier (NASDAQOTH:BDRBF) finally met its long-standing goal of lining up 300 firm orders for its brand-new CSeries jet. Its biggest coup was securing an order from airline giant Delta Air Lines (NYSE:DAL) for 75 CS100 jets, with options for another 50.

However, Bombardier had to offer a huge discount of 65% to 70% to land the Delta deal. At those prices, it will lose money. The company needs to bring in more CSeries orders in the coming years to fill out its backlog -- without conceding so much on price that it continues losing money on the CSeries program indefinitely.

Airline Delta Air Lines Dal Cseries Cs

Bombardier offered huge discounts to entice Delta to order the CS100 jet. Image source: Delta Air Lines.

Fast-growing U.S. budget carrier Spirit Airlines (NASDAQ:SAVE) -- which currently flies an all-Airbus (NASDAQOTH:EADSY) fleet -- has recently expressed interest in the CSeries jet. Could Spirit be the source of Bombardier's next big CSeries order?

Time to make a profit

After landing firm orders for 120 CSeries jets from Delta Air Lines and Air Canada earlier this year, Bombardier announced that it would record a special "onerous contract" charge of about $500 million.

In large part, this reflects a normal cost of doing business. Aircraft production costs decline over time as production processes become more efficient, so it's typical for early delivery slots to be sold below cost. Additionally, it's important for a new aircraft program to be backed by a few marquee customers to build credibility with other airlines and ensure that the necessary spare parts pools and maintenance expertise will be available.

Still, at the reported sub-$30 million price per aircraft that Delta negotiated, it would be very hard for Bombardier to turn a profit even with normalized production costs.

Right now, Bombardier has a little more than 300 unfilled firm CSeries orders (after excluding orders that are likely to be canceled). That's enough to fill most of its production capacity during the planned 2016-2020 production ramp period.

Bombardier Cseries

Bombardier needs to sell a lot of CSeries jets in the next few years. Image source: Bombardier.

By the end of 2020, Bombardier should reach a CSeries production rate of about 120 aircraft per year. It needs to gather a lot of orders in the next few years to fill all of those production slots. (It took eight years to line up the first several hundred CSeries orders.) Bombardier also needs to sell these slots at prices that will generate positive cash flow so that it can start to recoup its massive investment in the CSeries program.

Is Spirit Airlines a good prospect?

Spirit Airlines has been studying the CSeries jet since earlier this year, according to Bloomberg. During the company's earnings call last week, one analyst asked about the company's potential interest in adding CSeries jets to its fleet.

Spirit Airlines CEO Bob Fornaro responded that the company needs to place another major aircraft order relatively soon. Spirit plans to grow capacity 15% to 20% annually for at least the next five years -- and it will have plenty of room left for growth thereafter. Yet based on its current fleet plan, annual growth would drift down toward 10% by 2019 or 2020 -- and the carrier has no orders beyond 2021.

According to Fornaro, other manufacturers are likely to be aggressive in competing with Airbus for Spirit Airlines' business. Indeed, Airbus has a near-monopoly on the ultra-low cost carrier segment. Rivals like Bombardier can't afford to concede that whole market to Airbus, given that it will account for much of the airline industry's growth in the coming years.

The CSeries would also fit well with Spirit's current strategy. After a multiyear push toward flying larger planes (which typically have lower costs per seat) and focusing its growth in big cities, Spirit Airlines has started to seek out smaller markets where it will face less competition. To serve those routes appropriately, it is extending the life of its fleet of 145-seat Airbus A319s.

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Spirit is starting to use its A319s to serve smaller markets that it once ignored. Image source: Spirit Airlines.

In many ways, Bombardier's CSeries jets would be a more logical fit for these routes. The CS100 is somewhat smaller than the A319 while the CS300 is roughly comparable in size, and both models are significantly more fuel efficient than the A319. Furthermore, availability should start to improve around the time when Spirit will need more planes.

The downside is that adding a second aircraft type would increase complexity and training costs. Yet while most low-cost airlines stick to a uniform fleet, some have diversified into a second aircraft type successfully -- including Fornaro's former company, AirTran Airways.

Beating Airbus is a long shot

While Spirit Airlines is wisely studying the CSeries jet, it is more likely to use that as bargaining leverage with Airbus than to actually place an order with Bombardier. Spirit is a key customer for Airbus, given its leading position among U.S. ultra-low cost carriers. If Airbus allows Bombardier to gain a foothold, it could ultimately end up losing out on hundreds of future orders.

As a result, Airbus would probably be willing to sell A319neos at cost to maintain its exclusive relationship with Spirit Airlines. Bombardier wouldn't be able to match that price without taking more big losses, given Airbus' much greater manufacturing scale. And while the A319neo isn't as efficient as the CSeries jets, it's close enough that it would be hard to justify the additional complexity of operating a mixed fleet.

Bombardier has built a great airplane. But Boeing and Airbus are fierce competitors. If Bombardier's CSeries jet is to succeed, it probably won't be by peeling away customers like Spirit Airlines that have an entrenched single fleet type.

Adam Levine-Weinberg owns shares of Boeing and Spirit Airlines and is long December 2016 $30 calls on Spirit Airlines and long January 2017 $40 calls on Delta Air Lines. The Motley Fool recommends Spirit Airlines. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.