Shares of Firefly Aerospace Inc. (FLY) jumped 23.03% to $18.67 after the company announced a rocket engine agreement with satellite operator AST SpaceMobile valued at more than $1.3 billion. The stock gained $3.49 during the session and approached its intraday high of $18.70. The agreement underpins Firefly's manufacturing expansion while supporting AST SpaceMobile's heavy-lift rocket development program.

AST SpaceMobile, which is developing a space-based cellular broadband network, will take delivery of 36 engines for the first three rockets in its planned heavy-lift launch system.

36 Engines and a Manufacturing License

Under the agreement, Firefly will supply 36 rocket engines and engineering support over a three-year period. AST SpaceMobile will also receive a license to manufacture Firefly engines for its planned heavy-lift rockets, giving the satellite operator in-house production capability as it scales its launch program. The arrangement combines equipment deliveries, technical assistance, and manufacturing rights in a single framework.

For the first three rockets, Firefly will provide 27 Miranda engines and nine Vira vacuum engines. The engines will power AST SpaceMobile's new launch system, which is intended to let the company manage launch schedules directly instead of relying on outside providers.

Payments under the deal will exceed $1.3 billion, delivered through a combination of cash and AST SpaceMobile Class A shares. The stock component carries various lock-up periods, meaning the value of the equity portion to Firefly will be realized over time rather than at signing. Firefly, meanwhile, will retain ownership of its engine intellectual property, keeping those designs available for the commercial and government customers it plans to continue serving alongside the AST SpaceMobile work.

Testing Record Backs the Engine Commitments

Firefly developed Miranda as a high-thrust engine with a rated thrust of 230,000 pounds-force. The engine has completed more than 175 hot-fire tests, totaling over 4,200 seconds of operation, providing the technical foundation for the new engine commitments.

During one flight-like test, Miranda operated at 110% performance and exceeded its nominal flight duration, running 20 seconds beyond the planned 206-second interval.

Firefly also developed the Vira engine using technology drawn from its earlier Reaver and Lightning engines. Both newer engines build on the company's patented tap-off cycle and in-house development capabilities. Firefly designs, builds, and tests its propulsion systems internally, an approach that supports its existing government and commercial launch activities.

Production Expansion in Texas

Firefly plans to use the additional funds to expand hiring and purchase long-lead materials. The company will also acquire equipment and strengthen infrastructure to increase launch vehicle output, investments aimed at relieving production constraints as demand for launch services grows.

At its Briggs, Texas, facility, Firefly plans to add multiple engine testing bays. The added capacity will support more frequent testing and shorten production timelines across its launch programs. Firefly also expects its larger engineering team to advance milestones across its technology roadmap.

Both companies maintain headquarters in Texas and operate across different parts of the space industry. Firefly will continue serving other commercial customers and government programs under the agreement. The deal gives AST SpaceMobile access to engine manufacturing capabilities while providing Firefly with funding for its broader production plans in the years ahead. Over the agreement's three-year delivery window, the pace of engine shipments, the buildout of test bays at Briggs, and progress on the first three heavy-lift rockets will serve as concrete checkpoints on how the partnership develops.