Macquarie Infrastructure : MIC Proxy Statement - Special Meeting of Shareholders - 6 May 2021

PROPOSED REORGANIZATION - YOUR VOTE IS VERY IMPORTANT

Dear Macquarie Infrastructure Corporation Shareholder:

On behalf of the board of directors of Macquarie Infrastructure Corporation ("MIC Corp."), you are cordially invited to attend a special meeting of our shareholders to be held on May 6, 2021 at 3:00 p.m., Eastern time, in virtual format. Due to the ongoing and widespread impact of the coronavirus and to support the health and well-being of our shareholders, board, management and staff, this meeting will be a "virtual meeting" of shareholders, that is, you may participate solely "by means of remote communication." Enclosed you will find the notice of special meeting, proxy statement/prospectus and proxy card.

The board of directors of MIC Corp. has approved an agreement and plan of merger, dated as of March 30, 2021 (the "merger agreement"), by and among MIC Corp., Macquarie Infrastructure Holdings, LLC ("Holdings LLC"), a recently formed Delaware limited liability company and a wholly-owned subsidiary of MIC Corp., and Plum Merger Sub, Inc., a recently formed Delaware corporation and direct wholly- owned subsidiary of Holdings LLC ("Merger Sub"), providing for Merger Sub to merge with and into MIC Corp., currently a publicly-traded Delaware corporation, whereupon the separate corporate existence of Merger Sub will cease and MIC Corp. will be the surviving entity of the merger (the "merger"), resulting in MIC Corp. becoming a wholly-owned subsidiary of Holdings LLC, which will become publicly-traded as a result of the transactions described herein, subject to the satisfaction of certain closing conditions (including the approval of MIC Corp.'s shareholders). Upon the effectiveness of the merger, MIC Corp. common stock will be converted into Holdings LLC common units and stock certificates representing MIC Corp. common stock immediately prior to the merger will be deemed to represent Holdings LLC common units without an exchange of certificates. The number of Holdings LLC common units you will own following the consummation of the merger will be the same as the number of shares of common stock of MIC Corp. that you own immediately prior to the merger, and your relative economic ownership in the company will remain unchanged. We expect that Holdings LLC will issue 87,505,452 common units, based on the number of outstanding shares of MIC Corp. common stock as of March 29, 2021.

Following the consummation of the merger, it is anticipated that a direct subsidiary of MIC Corp. will distribute all of the limited liability company interests in MIC Hawaii Holdings, LLC ("MIC Hawaii") to MIC Corp., and MIC Corp. will in turn distribute such limited liability company interests to Holdings LLC (these distributions, the "Hawaii distribution" and, together with the merger, the "reorganization"). MIC Hawaii holds the businesses comprising MIC Corp.'s MIC Hawaii business segment.

Following the reorganization, it is anticipated that Holdings LLC will directly own (i) MIC Corp., which will continue to own the businesses comprising its Atlantic Aviation business segment and other assets currently owned by MIC Corp., and (ii) MIC Hawaii. MIC Corp.'s current management, including all directors and officers, will assume identical positions with Holdings LLC. In addition, Macquarie Infrastructure Management (USA) Inc., the manager of MIC Corp., will serve as the external manager of Holdings LLC on the same terms as it serves MIC Corp. We will apply to list Holdings LLC's common units to trade on the NYSE under the ticker symbol "MIC" as of the effective time of the merger (i.e., the acceptance of the certificate of merger by the Secretary of State of Delaware or at a later time if so specified in the certificate of merger).

The board of directors of MIC Corp. has determined that the merger agreement and the merger and the Hawaii distribution on the terms and conditions described herein, are advisable and in the best interests of MIC Corp. and its shareholders, and has unanimously approved the merger and the Hawaii distribution. You are only being asked to vote on the adoption of the merger agreement. Shareholder approval is required for the adoption of the merger agreement but is not required for the Hawaii distribution. If shareholders do not approve the adoption of the merger agreement, the Hawaii distribution will not occur. The board of directors of MIC Corp. recommends that you vote FOR the adoption of the merger agreement (the "merger proposal") and FOR the adjournment of the special meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the special meeting to approve the merger proposal (the "adjournment proposal").

The board of directors of MIC Corp. believes that the reorganization is beneficial because, as further described herein, it will provide flexibility to pursue the sale or sales of MIC Corp.'s remaining operating businesses in any sequence without altering the after-tax net proceeds to shareholders on the sale of our Atlantic Aviation business. Under our current corporate structure, a tax-efficient sale of the Atlantic Aviation business would require that such sale is consummated after the sale of MIC Hawaii, which in turn would

require approval from the Hawaii Public Utilities Commission ("HPUC"). Accordingly, under our current structure, the uncertainty and unknown length of time associated with the HPUC approval for a sale of MIC Hawaii could result in a significant delay to achieve a tax-efficient sale of our Atlantic Aviation business. The reorganization would facilitate the tax-efficient sale of the Atlantic Aviation business before the sale of MIC Hawaii, and without regard to the HPUC approval process or timeline. Following receipt of shareholder approval of the merger proposal, the board of directors intends to evaluate the status of efforts to sell MIC Corp. or its remaining operating businesses, and complete the reorganization at such time as it determines will be in the best interests of MIC Corp. and its shareholders. The board currently anticipates implementing the reorganization following execution of a definitive agreement for, and prior to completing, the sale of the Atlantic Aviation business. MIC Corp. has not entered into definitive agreements to sell any of its remaining operating businesses, and there can be no assurance as to whether, when or in what order any such agreement will be executed or that the reorganization will be completed.

Your vote is very important. MIC Corp. cannot consummate the merger unless, among other things, the holders of at least a majority of the voting power of MIC Corp. common stock issued and outstanding and entitled to vote thereon approve the merger proposal. MIC Corp. will hold a special meeting of shareholders (the "special meeting") to vote on the approval of the merger proposal and the adjournment proposal. The special meeting will be held at the date and time set forth below unless adjourned or postponed. Regardless of whether you plan to attend the special meeting, please take the time to submit your proxy by completing and mailing the enclosed proxy card. If you hold your shares through an account with a broker, bank or other nominee, please follow the instructions you receive from them to vote your shares.

The board of directors of MIC Corp. recommends that you vote FOR the merger proposal and FOR the adjournment proposal.

Before casting your vote, please take the time to review carefully the accompanying proxy statement/ prospectus, including the section entitled "Risk Factors" beginning on page 23 of the accompanying proxy statement/prospectus for a discussion of the risks relating to the merger.

On behalf of the board of directors and senior management of MIC Corp., I extend our appreciation for your participation and interest in MIC Corp.

Sincerely,

Martin Stanley	Norman H. Brown, Jr.
Chairman of the Board of Directors	Lead Independent Director

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued under the accompanying proxy statement/prospectus or the transactions contemplated thereby, has passed upon the merits or fairness of the transactions contemplated thereby, or has passed upon the adequacy or accuracy of the disclosure in the accompanying proxy statement/prospectus. Any representation to the contrary is a criminal offense.

MIC Corp. is not an authorized deposit-taking institution for the purposes of the Banking Act 1959 (Commonwealth of Australia) and its obligations do not represent deposits or other liabilities of Macquarie Bank Limited ABN 46 008 583 542, ("MBL"). MBL does not guarantee or otherwise provide assurance in respect of the obligations of MIC Corp.

The accompanying proxy statement/prospectus is dated April 5, 2021, and is first being mailed to MIC Corp.'s shareholders on or about April 5, 2021.

MACQUARIE INFRASTRUCTURE CORPORATION

April 5, 2021

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

To Be Held on May 6, 2021

Dear Shareholder:

You are cordially invited to attend the special meeting of shareholders of Macquarie Infrastructure Corporation ("MIC Corp." and, such meeting, the "special meeting"), to be held on May 6, 2021 at 3:00 p.m., Eastern time, in virtual format, to consider and vote upon the following matters:

1. A proposal to adopt the agreement and plan of merger, dated as of March 30, 2021 (as it may be amended from time to time, the "merger agreement"), by and among MIC Corp., Macquarie Infrastructure Holdings, LLC, a recently formed Delaware limited liability company ("Holdings LLC"), and Plum Merger Sub, Inc., a recently formed Delaware corporation (the "merger proposal"), providing for the merger of Merger Sub with and into MIC Corp., currently a publicly-traded Delaware corporation, whereupon the separate corporate existence of Merger Sub will cease and MIC Corp. will be the surviving entity of the merger (the "merger"), resulting in MIC Corp. becoming a wholly- owned subsidiary of Holdings LLC.
2. A proposal to adjourn the special meeting to a later date or dates, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the special meeting to approve the merger proposal (the "adjournment proposal").

The proposed merger is being undertaken to cause MIC Corp. to become a subsidiary of Holdings LLC. The board of directors reserves the right to abandon or postpone the merger at any time prior to the effective time of the merger, even after the shareholders have adopted the merger agreement at the special meeting and the other conditions to the completion of the merger have been satisfied or waived.

The foregoing matters are more fully described in the enclosed proxy statement/prospectus. The board

of directors of MIC Corp. recommends that you vote FOR the merger proposal and FOR the adjournment proposal.

The record date for the special meeting is March 29, 2021 (the "record date"). Only shareholders of record at the close of business on March 29, 2021 are entitled to notice of, and to vote at, the special meeting and at any subsequent adjournments or postponements thereof. All shareholders of record as of the record date are cordially invited to attend the special meeting online. Due to the ongoing and widespread impact of the coronavirus and to support the health and well-being of our shareholders, board, management and staff, this meeting will be a "virtual meeting" of shareholders, meaning that you may participate solely "by means of remote communication." Each shareholder of record who owns common stock of MIC Corp. (the "common stock") on the record date and is present in person (which in this instance means presence at the virtual meeting) or represented by proxy is entitled to one vote for each share of common stock.

The share register will not be closed between the record date and the date of the special meeting. A list of the shareholders entitled to vote at the special meeting will be available for inspection during the ten days prior to the special meeting at our principal executive offices at 125 West 55th Street, New York, New York 10019 and will be available during the meeting at www.virtualshareholdermeeting.com/MIC21SM.

Your vote is very important. MIC Corp. cannot complete the merger unless, among other things, the holders of at least a majority of the shares of MIC Corp. common stock issued and outstanding and entitled to vote thereon vote to approve the merger proposal.

You will be able to attend the special meeting online, vote your shares electronically and submit questions during the special meeting, by visiting www.virtualshareholdermeeting.com/MIC21SM. You will need your 16-Digit Control Number to enter the special meeting in this manner. In addition, you may listen to the meeting via conference call at (USA) [phone] or (International) 1-236-714-3310, passcode 3653458. Please note that you will not be able to submit questions or vote your shares via conference call. Regardless of whether you plan to attend the special meeting online, please take the time to submit your proxy

by completing and mailing the enclosed proxy card. If you hold your shares through an account with a broker, bank or other nominee, please follow the instructions you receive from them to vote your shares. If you fail to submit a proxy or to attend the special meeting online or do not provide your broker, bank or other nominee with instructions as to how to vote your shares, such action will have the effect of a vote "AGAINST" the merger proposal. If you fail to submit a proxy or to attend the special meeting online or do not provide your broker, bank or other nominee with instructions as to how to vote your shares, such action will not have an effect on a vote to approve the adjournment proposal.

Please read carefully the sections in the proxy statement/prospectus on attending and voting at the special meeting to ensure that you comply with any applicable requirements.

WHETHER OR NOT YOU PLAN TO ATTEND THE SPECIAL MEETING, PLEASE COMPLETE, DATE, SIGN AND RETURN, AS PROMPTLY AS POSSIBLE, THE ENCLOSED PROXY CARD IN THE ACCOMPANYING PREPAID REPLY ENVELOPE, OR SUBMIT YOUR PROXY BY TELEPHONE OR THE INTERNET. IF YOU ATTEND THE SPECIAL MEETING AND VOTE ONLINE, YOUR VOTE BY BALLOT WILL REVOKE ANY PROXY PREVIOUSLY SUBMITTED.

The proxy statement/prospectus and the enclosed proxy card are available on our web site at

www.macquarie.com/mic under "Investor Center/Shareholder Meetings."

By Order of the Board of Directors,

Michael Kernan

General Counsel and Secretary

REFERENCES TO ADDITIONAL INFORMATION

This proxy statement/prospectus incorporates by reference important business and financial information about MIC Corp. from other documents filed with the Securities and Exchange Commission (the "SEC") that are not included or delivered with this proxy statement/prospectus. See the section entitled "Where You Can Find More Information; Incorporation by Reference" beginning on page 93 of this proxy statement/ prospectus for a list of the documents incorporated by reference into this proxy statement/prospectus.

Documents incorporated by reference are available to you without charge upon oral or written request. You can obtain any of these documents by requesting them in writing or by telephone from MIC Corp. at the following address and telephone number:

Macquarie Infrastructure Corporation

125 West 55th Street

New York, NY 10019

[phone]

To receive timely delivery of the requested documents in advance of the special meeting, you should make your request no later than April 29, 2021.

You may also obtain free copies of the documents filed by MIC Corp. with the SEC at the SEC's website, www.sec.gov. Please visit the SEC's website for additional information.

Information contained on MIC Corp.'s website and any other website is not incorporated by reference herein.

ABOUT THIS PROXY STATEMENT/PROSPECTUS

This document, which forms part of a registration statement on Form S-4 filed with the SEC by Holdings LLC (File No. 333-253193), constitutes a prospectus of Holdings LLC under Section 5 of the Securities Act of 1933, as amended, with respect to the common units of Holdings LLC to be issued to shareholders of MIC Corp. in connection with the merger. This document also constitutes a notice of meeting and proxy statement under Section 14(a) of the Securities Exchange Act of 1934, as amended, with respect to the special meeting, at which MIC Corp.'s shareholders will be asked to consider and vote on the proposal to adopt the merger agreement.

You should rely only on the information contained in, or incorporated by reference into, this document. Neither MIC Corp. nor Holdings LLC has authorized anyone to provide you with information that is different from that contained in, or incorporated by reference into, this document. This document is dated April 5, 2021. The information contained in this document is accurate only as of that date or in the case of information in a document incorporated by reference, as of the date of such document, unless the information specifically indicates that another date applies. Neither the mailing of this document to MIC Corp. shareholders nor the taking of any actions contemplated hereby by MIC Corp. or Holdings LLC at any time will create any implication to the contrary.