UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE

SECURITIES EXCHANGE ACT OF 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant  ☐

Check the appropriate box:

ALTAIR ENGINEERING INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

[The following material was used by Altair Engineering Inc. (“Altair”) in its discussion with employees, in connection with the proposed acquisition of Altair by Siemens Industry Software Inc.]

Dear Altairians,

As I am sure you have all heard, Altair signed a definitive agreement with siemens to merge the company into Siemens AG, Digital Industries Division, as part of their software business.

The deal was signed on today, October 30 and will begin a period to clear regulatory compliances in several countries and is expected to close within the second half of 2025. Our board deliberated carefully in reaching its decision to approve this transaction.

Altair was a major part of my life and all of you are an extended family for me all around the world. I took energy every day by interacting with you and seeing the passion, creativity, and excitement you brought to your work, whether developing a new capability in our software, helping customers solve problems, or competing to win business against others. And I am so grateful to all of you and to the Altairians who came before you and retired or left.

I believe Siemens PLM is the perfect acquirer for Altair. Siemens is strong on both the mechanical and electronics side and has a strong philosophy of open solutions similar to Altair’s. Their culture is technical, and they have excellent products for MCAD, ECAD, PLM, and general purpose CFD. They also acquired Mendix, a leading software for low code (drag and drop) development of applications. They also play in a broad range of markets including traditional manufacturing, but also health care and BFSI. Their automation business sells to all these players and is very strong in manufacturing across all industries. Altair brings to the table all simulation beyond general purpose CFD, data analytics and data science including the work we have done with engineering, and the HPC technology and expertise key for making everything work.

I believe this combination will be a force in a market where convergence is key. They bring the scale and top-down selling relationships, while we bring deep knowledge and technology growing in relevance and the strong relationships with the experts across organizations.

During this period before closing, we will operate normally, and I sincerely appreciate that all of you will continue to work to “keep the trains running on time”.

I plan to hold a town hall meeting tomorrow (to be announced) to discuss the merger more and to answer questions.

As always, thank you for your support!

JimS

Important Information and Where to Find It

This communication relates to a proposed transaction between Altair and Siemens Industry Software Inc. (“Parent”). In connection with this proposed transaction, Altair has filed a Current Report on Form 8-K with further information regarding the terms and conditions contained in the definitive transaction agreements and will file a proxy statement on Schedule 14A or other documents with the United States Securities and Exchange Commission (the “SEC”). This communication is not a substitute for any proxy statement or other document that Altair may file with the SEC in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS OF ALTAIR ARE URGED TO READ THE PROXY STATEMENT, INCLUDING THE DOCUMENTS INCORPORATED BY REFERENCE INTO THE PROXY STATEMENT, AND OTHER DOCUMENTS THAT MAY BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION. The definitive proxy statement, when available, will be mailed to stockholders of Altair as applicable. Investors and security holders will be able to obtain free copies of these documents, when available, and other documents filed with the SEC by Altair through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Altair will be available free of charge on

Altair’s internet website at https://investor.altair.com or by contacting Altair’s primary investor relations contact by email at ir@altair.com or by phone at (248) 614-2400.

Participants in Solicitation

Altair, Parent, Siemens AG, their respective directors and certain of their respective executive officers may be considered participants in the solicitation of proxies in connection with the proposed transaction. Information about the directors and executive officers of Altair, their ownership of Altair common shares, and Altair’s transactions with related persons is set forth in its Annual Report on Form 10-K for the fiscal year ended December 31, 2023, which was filed with the SEC on February 22, 2024 (and which is available at  https://www.sec.gov/ix?doc=/Archives/edgar/data/0001701732/000095017024018804/altr-20231231.htm), in its proxy statement on Schedule 14A for its 2024 Annual Meeting of Stockholders in the sections entitled “Corporate Governance Matters,” “Security Ownership of Certain Beneficial Owners and Management” and “Transactions with Related Persons”, which was filed with the SEC on April 5, 2024 (and which is available at  https://www.sec.gov/ix?doc=/Archives/edgar/data/0001701732/000119312524087903/d722499ddef14a.htm), certain of its Quarterly Reports on Form 10-Q and certain of its Current Reports on Form 8-K.

These documents can be obtained free of charge from the sources indicated above. Additional information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the proxy statement and other relevant materials to be filed with the SEC when they become available.

No Offer or Solicitation

This communication is for informational purposes only and is not intended to and shall not constitute an offer to buy or sell or the solicitation of an offer to buy or sell any securities, or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.

Forward Looking Statements

This communication contains “forward-looking statements” within the Private Securities Litigation Reform Act of 1995. Any statements contained in this communication that are not statements of historical fact, including statements regarding the proposed transaction, including the expected timing and closing of the proposed transaction; Altair’s ability to consummate the proposed transaction; the expected benefits of the proposed transaction and other considerations taken into account by the Altair Board of Directors in approving the proposed transaction; the amounts to be received by stockholders and expectations for Altair prior to and following the closing of the proposed transaction, may be deemed to be forward-looking statements. All such forward-looking statements are intended to provide management’s current expectations for the future of Altair based on current expectations and assumptions relating to Altair’s business, the economy and other future conditions. Forward-looking statements generally can be identified through the use of words such as “believes,” “anticipates,” “may,” “should,” “will,” “plans,” “projects,” “expects,” “expectations,” “estimates,” “forecasts,” “predicts,” “targets,” “prospects,” “strategy,” “signs,” and other words of similar meaning in connection with the discussion of future performance, plans, actions or events. Because forward-looking statements relate to the future, they are subject to inherent risks, uncertainties and changes in circumstances that are difficult to predict. Such risks and uncertainties include, among others: (i) the timing to consummate the proposed transaction, (ii) the risk that a condition of closing of the proposed transaction may not be satisfied or that the closing of the proposed transaction might otherwise not occur, (iii) the risk that a regulatory approval that may be required for the proposed transaction is not obtained or is obtained subject to conditions that are not anticipated, (iv) the diversion of management time on transaction-related issues, (v) risks related to disruption of management time from ongoing business operations due to the proposed transaction, (vi) the risk that any announcements relating to the proposed transaction could have adverse effects on the market price of the common stock of Altair, (vii) the risk that the proposed transaction and its announcement could have an adverse effect on the ability of Altair to retain customers and retain and hire key personnel and maintain relationships with its suppliers and customers, (viii) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the Merger Agreement, dated October 30, 2024, with Siemens (the “Merger Agreement”), including in circumstances requiring Altair to pay a termination fee, (ix) the risk that

competing offers will be made; (x) unexpected costs, charges or expenses resulting from the merger, (xi) potential litigation relating to the merger that could be instituted against the parties to the Merger Agreement or their respective directors, managers or officers, including the effects of any outcomes related thereto, (xii) worldwide economic or political changes that affect the markets that Altair’s businesses serve which could have an effect on demand for Altair’s products and impact Altair’s profitability and (xiii) disruptions in the global credit and financial markets, including diminished liquidity and credit availability, changes in international trade agreements, including tariffs and trade restrictions, cyber-security vulnerabilities, foreign currency volatility, swings in consumer confidence and spending, raw material pricing and supply issues, retention of key employees, increases in fuel prices, and outcomes of legal proceedings, claims and investigations. Accordingly, actual results may differ materially from those contemplated by these forward-looking statements. Investors, therefore, are cautioned against relying on any of these forward-looking statements. They are neither statements of historical fact nor guarantees or assurances of future performance. Additional information regarding the factors that may cause actual results to differ materially from these forward-looking statements is available in Altair’s filings with the SEC, including the risks and uncertainties identified in Part I, Item 1A—Risk Factors of Altair’s Annual Report on Form 10-K for the year ended December 31, 2023 and in Altair’s other filings with the SEC. The list of factors is not intended to be exhaustive.

These forward-looking statements speak only as of the date of this communication, and Altair does not assume any obligation to update or revise any forward-looking statement made in this communication or that may from time to time be made by or on behalf of Altair.