Firefly Aerospace美股招股说明书(2026-06-02版)

11,111,116 Shares This prospectus supplement updates and supplements the prospectus dated December19, 2025, as supplemented or amended from time to time (the“Prospectus”), which forms a part of our Registration Statement on Form S-1 (Registration No.333-291599). This prospectus supplement is being filedto update and supplement the information in the Prospectus with the information contained in our Current Report on Form 8-K, filed with the Securitiesand Exchange Commission on June2, 2026 (the “Current Report”). Accordingly, we have attached the Current Report to this prospectus supplement. The Prospectus relates to the offer and sale from time to time by the selling securityholders named in the Prospectus (the “Selling Securityholders”) ofup to 11,111,116 shares of Common Stock, par value $0.0001 per share (the “Common Stock”) of Firefly Aerospace Inc. (“Firefly Aerospace”) that werereceived by such Selling Securityholders as consideration in connection with Firefly Aerospace’s acquisition of SciTec Innovations, LLC, a Delawarelimited liability company. This prospectus supplement should be read in conjunction with the Prospectus. This prospectus supplement updates and supplements the information inthe Prospectus. If there is any inconsistency between the information in the Prospectus and this prospectus supplement, you should rely on theinformation in this prospectus supplement. Our Common Stock is listed on the Nasdaq Global Market under the symbol “FLY”. On June1, 2026, the closing price of our Common Stock was$44.24 per share. Investing in our Common Stock involves risks. See “Risk Factors” beginning on page 9 of the Prospectus, and undersimilar headings in any further amendments or supplements to the Prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities ordetermined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense. UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 FORM 8-K CURRENT REPORTPursuant to Section 13 OR 15(d)of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 28, 2026 Firefly Aerospace Inc.(Exact name of registrant as specified in its charter) 001-42789(CommissionFile Number) 81-5194980(IRS EmployerIdentification No.) 2203 Scottsdale DriveLeander, Texas(Address of principal executive offices) 78641(Zip Code) Registrant’s telephone number, including area code: (512) 893-5570 N/A(Former name or former address, if changed since last report.) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of thefollowing provisions: ☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of thischapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company☒ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with anynew or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ Item 1.01.Entry into a Material Definitive Agreement. On May28, 2026, Firefly Aerospace Inc. (the “Company”) priced the previously announced offering (the “Offering”) of its common stock, par value$0.0001 per share (the “Common Stock”), at a public offering price of $48.00 per share (the “Offering Price”), pursuant to the Company’s registrationstatement on FormS-1 (FileNo.333-296233) (the “Registration Statement”). On May28, 2026, in connection with the pricing of the Offering, theCompany entered into an underwriting agreement (the “Underwriting Agreement”) with Goldman Sachs& Co. LLC, J.P. Morgan Securities LLC,Jefferies LLC and Wells Fargo Securities, LLC, as representatives of the several underwriters listed on Schedule I thereto (collectively, the“Underwriters”), and the selling stockholders listed on Schedule II thereto (the “Selling Stockholders”), pursuant to which the Company agreed to offerand sell 4,000,000 shares of Common Stock and the Selling Stockholders agreed to sell 8,000,000 shares of Common Stock at the Offering Price. TheSelling Stockholders granted the Underwriters a30-dayoption to purchase up to an additional 1,800,000 shares of Common Stock. The Offering closedand the shares were del