$1,000,000 Promissory Note dated September 27, 2021

Exhibit 10.18

THIS PROMISSORY NOTE (“NOTE”) HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”).  THIS NOTE HAS BEEN ACQUIRED FOR INVESTMENT ONLY AND MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED IN THE ABSENCE OF REGISTRATION OF THE RESALE THEREOF UNDER THE SECURITIES ACT OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY IN FORM, SCOPE AND SUBSTANCE TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.  

PROMISSORY NOTE

Yellowstone Acquisition Company, a Delaware corporation (“Maker”), promises to pay to the order of BOC Yellowstone LLC, a Delaware limited liability company, or its registered assigns or successors in interest or order (“Payee”), the principal sum of up to One Million Dollars ($1,000,000.00), together with all accrued interest thereon, in lawful money of the United States of America, on the terms and conditions described below.  All payments on this Note (unless the full principal amount, together with all accrued interest thereon, is converted pursuant to Section 15 below) shall be made by check or wire transfer of immediately available funds to such account as Payee may from time to time designate by written notice in accordance with the provisions of this Note.

1.         Payment. All payments of interest and principal provided for in this Note shall be payable on the earliest to occur of (i) the date on which Maker consummates its initial business combination and (ii) the date that the winding up of Maker is effective (such date, the “Maturity Date”). The principal balance, together with all accrued interest thereon, may be prepaid at any time, at the election of Maker.

2.         Interest. The outstanding principal amount hereunder shall bear interest at a rate per annum equal to the Applicable Federal Rate from the date of this Note through such date as it is paid in full. As used herein, “Applicable Federal Rate” means a rate of interest equal to the Federal Short Term Rate published pursuant to Section 1274(d) of the Code, compounded annually. Interest will only be payable upon demand. In no event shall interest exceed the maximum legal rate permitted by law. All computations of interest shall be made on the basis of 365 or 366 days, as the case may be, and the actual number of days elapsed. Interest shall accrue beginning on the date hereof, and shall not accrue on the date the amount under this Note is paid.

3.         Drawdown Requests. Payee, in its sole and absolute discretion, may fund the principal amount of up to One Million Dollars ($1,000,000.00) for costs reasonably related to Maker’s consummation of an initial business combination as contemplated by its initial public offering prospectus (the “initial business combination”). The principal of this Note may be drawn down from time to time until the date on which Maker consummates its initial business combination, upon written request from Maker to Payee (each, a “Drawdown Request”). Each Drawdown Request must state the amount to be drawn down, and must be in multiples of not less than Ten Thousand Dollars ($10,000) unless agreed upon by Maker and Payee. Payee, in its sole discretion, shall fund each Drawdown Request no later than five (5) business days after receipt of a Drawdown Request; provided, however, that the maximum principal amount of drawdowns collectively under this Note shall not exceed One Million Dollars ($1,000,000.00). Once an amount is drawn down under this Note, it shall not be available for future Drawdown Requests even if prepaid. Except as set forth herein, no fees, payments or other amounts shall be due to Payee in connection with, or as a result of, any Drawdown Request by Maker.

4.         Application of Payments. All payments of interest and principal received by Payee pursuant to this Note shall be applied first to the payment in full of any costs incurred in the collection of any sum due under this Note, including (without limitation) reasonable attorney’s fees, and then to the reduction of the unpaid principal balance of this Note.

5.         Events of Default. The following shall constitute an event of default (“Event of Default”):

(a) Failure to Make Required Payments. Failure by Maker to pay when due any amount of the unpaid principal balance or accrued and unpaid interest thereon owing under this Note within five (5) business days of the Maturity Date.

(b) Voluntary Bankruptcy, etc. The commencement by Maker of a voluntary case under any applicable bankruptcy, insolvency, reorganization, rehabilitation or other similar law, or the consent by it to the appointment of or taking possession by a receiver, liquidator, assignee, trustee, custodian, sequestrator (or other similar official) of Maker or for any substantial part of its property, or the making by it of any assignment for the benefit of creditors, or the failure of Maker generally to pay its debts as such debts become due, or the taking of corporate action by Maker in furtherance of any of the foregoing. 

(c) Involuntary Bankruptcy, Etc. The entry of a decree or order for relief by a court having jurisdiction in the premises in respect of Maker in an involuntary case under any applicable bankruptcy, insolvency or other similar law, or appointing a receiver, liquidator, assignee, custodian, trustee, sequestrator (or similar official) of Maker or for any substantial part of its property, or ordering the winding-up or liquidation of its affairs, and the continuance of any such decree or order unstayed and in effect for a period of 60 consecutive days.

(a) Upon the occurrence of an Event of Default specified in Section 5(a) hereof, Payee may, by written notice to Maker, declare this Note to be due immediately and payable, whereupon the unpaid principal amount of this Note and all other amounts payable hereunder (including accrued and unpaid interest), shall become immediately due and payable without presentment, demand, protest or other notice of any kind, all of which are hereby expressly waived, anything contained herein or in the documents evidencing the same to the contrary notwithstanding.

(b) Upon the occurrence of an Event of Default specified in Sections 5(b) and 5(c) hereof, the unpaid principal balance of this Note and all other amounts payable hereunder (including accrued and unpaid interest thereon), shall automatically and immediately become due and payable, in all cases without any action on the part of Payee.

7.         Waivers. Maker and all endorsers and guarantors of, and sureties for, this Note waive presentment for payment, demand, notice of dishonor, protest, and notice of protest with regard to this Note, all errors, defects and imperfections in any proceedings instituted by Payee under the terms of this Note, and all benefits that might accrue to Maker by virtue of any present or future laws exempting any property, real or personal, or any part of the proceeds arising from any sale of any such property, from attachment, levy or sale under execution, or providing for any stay of execution, exemption from civil process, or extension of time for payment; and Maker agrees that any real or personal property that may be levied upon pursuant to a judgment obtained by virtue hereof, on any writ of execution issued hereon, may be sold upon any such writ in whole or in part in any order desired by Payee.

8.         Unconditional Liability. Maker hereby waives all notices in connection with the delivery, acceptance, performance, default, or enforcement of the payment of this Note, and agrees that its liability shall be unconditional, without regard to the liability of any other party, and shall not be affected in any manner by any indulgence, extension of time, renewal, waiver or modification granted or consented to by Payee, and consents to any and all extensions of time, renewals, waivers, or modifications that may be granted by Payee with respect to the payment or other provisions of this Note, and agrees that additional makers, endorsers, guarantors, or sureties may become parties hereto without notice to Maker or affecting Maker’s liability hereunder.

9.         Notices. All notices, statements or other documents which are required or contemplated by this Note shall be: (i) in writing and delivered personally or sent by first class registered or certified mail, overnight courier service or facsimile or electronic transmission to the address designated in writing, (ii) by facsimile to the number most recently provided to such party or such other address or fax number as may be designated in writing by such party and (iii) by electronic mail, to the electronic mail address most recently provided to such party or such other electronic mail address as may be designated in writing by such party.  Any notice or other communication so transmitted shall be deemed to have been given on the day of delivery, if delivered personally, on the business day following receipt of written confirmation, if sent by facsimile or electronic transmission, one (1) business day after delivery to an overnight courier service or five (5) days after mailing if sent by mail.

10.         Construction. THIS NOTE SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF DELAWARE, WITHOUT REGARD TO THE CONFLICT OF LAWS PROVISIONS THEREOF.

11.         Severability. Any provision contained in this Note which is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction.

12.         Trust Waiver.   Notwithstanding anything herein to the contrary, Payee hereby waives any claim in or to any distribution of or from the trust account (the “Trust Account”) established in connection with Maker’s initial public offering (the “IPO”) or any distributions to its public stockholders therefrom, and hereby agrees not to seek recourse, reimbursement, payment or satisfaction for any claim against the Trust Account or any distributions to its public stockholders therefrom for any reason whatsoever; provided, however, that upon the consummation of the initial business combination, Maker shall repay the principal balance of this Note, together with all accrued and unpaid interest thereon, first using the proceeds released to Maker from the Trust Account and not distributed to its public stockholders.

13.         Amendment; Waiver.  Any amendment hereto or waiver of any provision hereof may be made with, and only with, the written consent of Maker and Payee.

14.         Assignment.  No assignment or transfer of this Note or any rights or obligations hereunder may be made by any party hereto (by operation of law or otherwise) without the prior written consent of the other party hereto and any attempted assignment without the required consent shall be void; provided, however, that the foregoing shall not apply to an affiliate of Payee who agrees to be bound to the terms of this Note.

15.         Conversion.

(a) Notwithstanding anything contained in this Note to the contrary, at Payee’s option, at any time prior to payment in full of principal amount under this Note, together with all accrued interest thereon , Payee may elect to convert all or any portion of the unpaid principal balance of this Note, together with all accrued and unpaid interest thereon, into that number of warrants, each whole warrant exercisable for one ordinary share of the Maker (the “Conversion Warrants”), equal to: (x) the portion of the principal amount of this Note, together with all accrued and unpaid interest thereon, being converted pursuant to this Section 15, divided by (y) $1.50, rounded up to the nearest whole number of warrants. The Conversion Warrants shall be identical to the warrants issued by the Maker to the Payee in a private placement upon consummation of the Maker’s initial public offering. The Conversion Warrants and the ordinary shares issuable upon the exercise of the Conversion Warrants, and any other equity security of Maker issued or issuable with respect to the foregoing by way of a share dividend or share split or in connection with a combination of shares, recapitalization, amalgamation, consolidation or reorganization, shall be entitled to the registration rights set forth in Section 16 hereof.

(b) Upon any complete or partial conversion of the principal amount of this Note, together with accrued by unpaid interest thereon, (i) such owed amount shall be so converted and such converted portion of this Note shall become fully paid and satisfied, (ii) Payee shall surrender and deliver this Note, duly endorsed, to Maker or such other address which Maker shall designate against delivery of the Conversion Warrants, (iii) Maker shall promptly deliver a new duly executed Note to Payee in the principal amount, together with all accrued and unpaid interest thereon, that remains outstanding, if any, after any such conversion and (iv) in exchange for all or any portion of the surrendered Note, Maker shall, at the direction of Payee, deliver to Payee (or its members or their respective affiliates) (Payee or such other persons, the “Holders”) the Conversion Warrants, which shall bear such legends as are required, in the opinion of counsel to Maker or by any other agreement between Maker and Payee and applicable state and federal securities laws.

(c) The Holders shall pay any and all issue and other taxes that may be payable with respect to any issue or delivery of the Conversion Warrants upon conversion of this Note pursuant hereto; provided, however, that the Holders shall not be obligated to pay any transfer taxes resulting from any transfer requested by the Holders in connection with any such conversion.

(d) The Conversion Warrants shall not be issued upon conversion of this Note unless such issuance and such conversion comply with all applicable provisions of law.

16.         Registration Rights.

(a) Reference is made to that certain Registration Rights Agreement between Maker and the parties thereto, dated as of October 21, 2020 (the “Registration Rights Agreement”). All capitalized terms used in this Section 16 shall have the same meanings ascribed to them in the Registration Rights Agreement.

(b) The Holders shall be entitled to one Demand Registration, which shall be subject to the same provisions as set forth in Section 2.1 of the Registration Rights Agreement.

(c) The Holders shall also be entitled to include the Conversion Warrants and the ordinary shares issuable upon the exercise of the Conversion Warrants in Piggyback Registrations, which shall be subject to the same provisions as set forth in Section 2.2 of the Registration Rights Agreement; provided, however, that in the event that an underwriter advises Maker that the Maximum Number of Securities has been exceeded with respect to a Piggyback Registration, the Holders shall not have any priority for inclusion in such Piggyback Registration.

(d) Except as set forth above, the Holders and Maker, as applicable, shall have all of the same rights, duties and obligations set forth in the Registration Rights Agreement.

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IN WITNESS WHEREOF, Maker, intending to be legally bound hereby, has caused this Note to be duly executed by the undersigned as of the day and year first above written.

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