JetBlue Airways Corp. says the biggest hindrances to its growth are continued delays in aircraft deliveries, and planes that it has been forced to park while waiting for engines or repairs.

The airline has said it will get just 19 new Airbus SE aircraft in 2023, instead of the 30 it originally expected. And July’s discovery of problems with some Pratt & Whitney parts affects some JetBlue engines that will have to be taken off planes by the middle of September.

The carrier is counting on acquiring rival Spirit Airlines Inc., to make it the fifth-largest U.S. carrier. But a legal challenge by the U.S. Justice Department on the grounds that the deal would violate federal anti-trust laws means that, for now, JetBlue has to maintain an alternate standalone plan for expansion. The airline needs to be larger to compete more effectively with carriers like American Airlines Group Inc. and Delta Air Lines Inc.

“We have a very big order book of new airplanes, but they’re all coming late,” chief executive officer Robin Hayes said in an interview with Matt Miller for Bloomberg Chief Future Officer. “On top of that, there are some engine issues. And so, we actually have airplanes on the ground today with no engines because there aren’t enough engines to support them. I would say right now that is the biggest inhibitor to that organic plan.”

Read more: Boeing Warns 737 Deliveries to Be at Low End of 2023 Target

Chief financial officer Ursula Hurley has said JetBlue now expects to receive 30 new planes in 2024, down from its original order of 43. But this was before factoring in the latest issue of potentially faulty Pratt & Whitney parts.

On September 11, RTX Corp. expanded the scope of required engine checks and said it would affect nearly its entire fleet of turbines powering Airbus’s latest A320. JetBlue had already been working with Pratt, a unit of RTX, to determine if its fleet of A220 aircraft also were affected. It has tried to lease extra engines, but the available supply is limited.

In August, JetBlue had two Airbus A321neo planes that had been grounded “for the last few months” on engine issues, with the number of parked planes expected to approximately double through the end of 2023, she said. JetBlue declined to provide an exact count.

“We will need to get creative on how we source airplanes in order to continue the JetBlue growth trajectory,” Hurley said in the Bloomberg TV interview. “We need to be very flexible in terms of our planning assumptions, and we very much value transparency from the manufacturers.”

Airbus slashed its annual delivery target twice in 2022 because of shortages in components ranging from seats to semiconductors to raw materials. The resulting delays have also affected operations at carriers including Spirit, Germany’s Deutsche Lufthansa AG and Hungary’s Wizz Air Holdings Plc.