UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 7)*

ALTAIR ENGINEERING INC.

(Name of Issuer)

CLASS A COMMON STOCK, $0.0001 PAR VALUE PER SHARE

(Title of Class of Securities)

021369103

(CUSIP Number)

September 30, 2024

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule 13G is filed:

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

☒ Rule 13d-1(d)

*	The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 021369103

Based on the information provided by Altair Engineering Inc. (the “Company”) to the Reporting Persons (as defined below), on September 30, 2024 (the “Event Date”), there were 59,517,279 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding. George J. Christ (“Mr. Christ”) is the Trustee of the Christ Revocable Trust dated May 8, 2015 (the “Christ Trust”), and the Manager of GC Investments, LLC (the “GC LLC” and, collectively with Mr. Christ and the Christ Trust, the “Reporting Persons”). Mr. Christ is also the Co-Trustee of The Dana Christ Irrevocable Trust Dated May 8, 2015 (the “Dana Trust”) and the Co-Trustee of The Lauren Christ Irrevocable Trust Dated May 8, 2015 (the “Lauren Trust”). As of the Event Date, the Reporting Persons may be deemed to beneficially own an aggregate of 9,450,684 shares of Class A Common Stock. The number of shares of Class A Common Stock reported above consists of (i) 4,481,778 shares of Class A Common Stock issuable upon conversion of 4,481,778 shares of the Company’s Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company held by the Christ Trust, (ii) 4,044,004 shares of Class A Common Stock issuable upon conversion of 4,044,004 shares of Class B Common Stock held by the GC LLC, (iii) 400,000 shares of Class A Common Stock held by the GC LLC, (iv) 149,954 shares of Class A Common Stock held by the Christ Trust, (v) 187,475 shares of Class A Common Stock held by the Dana Trust and (vi) 187,475 shares of Class A Common Stock held by the Lauren Trust. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Persons, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the Reporting Persons may be deemed to beneficially own 13.9% of the shares of Class A Common Stock issued and outstanding. The percentage was obtained by dividing (a) the number of shares of Class A Common Stock beneficially owned by the Reporting Persons as set forth in Row 9 by (b) the sum of (i) 59,517,279 shares of Class A Common Stock outstanding as of the Event Date and (ii) the 8,525,782 shares of Class A Common Stock issuable upon conversion of the Class B Common Stock.

CUSIP No. 021369103

Based on the information provided by Altair Engineering Inc. (the “Company”) to the Reporting Person (as defined below), on September 30, 2024 (the “Event Date”), there were 59,517,279 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding. George J. Christ (“Mr. Christ”) is the Trustee of the Christ Revocable Trust dated May 8, 2015 (the “Christ Trust”). As of the Event Date, the Christ Trust may be deemed to beneficially own an aggregate of 4,481,778 shares of Class A Common Stock. The number of shares of Class A Common Stock reported above consists of 4,481,778 shares of Class A Common Stock issuable upon conversion of 4,481,778 shares of the Company’s Class B common stock, $0.0001 par value per share (the “Class B Common Stock”). The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Person, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the Christ Trust may be deemed to beneficially own 7.0% of the shares of Class A Common Stock issued and outstanding. The percentage was obtained by dividing (a) the number of shares of Class A Common Stock beneficially owned by the Christ Trust as set forth in Row 9 by (b) the sum of (i) 59,517,279 shares of Class A Common Stock outstanding as of the Event Date and (ii) the 4,481,778 shares of Class A Common Stock issuable upon conversion of the Class B Common Stock beneficially owned by the Christ Trust.

CUSIP No. 021369103

Based on the information provided by Altair Engineering Inc. (the “Company”) to the Reporting Person (as defined below), on September 30, 2024 (the “Event Date”), there were 59,517,279 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”), outstanding. George J. Christ (“Mr. Christ”) is the Manager of GC Investments, LLC (the “GC LLC”). As of the Event Date, the GC LLC may be deemed to beneficially own an aggregate of 4,044,004 shares of Class A Common Stock. The number of shares of Class A Common Stock reported above consists of 4,044,004 shares of Class A Common Stock issuable upon conversion of 4,044,004 shares of the Company’s Class B common stock, $0.0001 par value per share (the “Class B Common Stock”). The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Person, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the GC LLC may be deemed to beneficially own 6.4% of the shares of Class A Common Stock issued and outstanding. The percentages were obtained by dividing (a) the number of shares of Class A Common Stock beneficially owned by the GC LLC as set forth in Row 9 by (b) the sum of (i) 59,517,279 shares of Class A Common Stock outstanding as of the Event Date and (ii) the 4,044,004 shares of Class A Common Stock issuable upon conversion of the Class B Common Stock beneficially owned by the GC LLC.

Item 1(a).

Name Of Issuer:

Altair Engineering Inc. (the “Company”)

Item 1(b).

Address of Issuer’s Principal Executive Offices:

1820 E. Big Beaver Road

Troy, MI 48083

Item 2(a).

Name of Person Filing:

This report on Schedule 13G (this “Schedule 13G”), is being jointly filed by (i) Christ Revocable Trust dated May 8, 2015 (the “Christ Trust”), (ii) GC Investments, LLC (the “GC LLC”), and (iii) George J. Christ as the Trustee of the Christ Trust, the Manager of the GC LLC, the Co-Trustee of The Dana Christ Irrevocable Trust Dated May 8, 2015 (the “Dana Trust”) and the Co-Trustee of The Lauren Christ Irrevocable Trust Dated May 8, 2015 (the “Lauren Trust”) (“Mr. Christ” and, collectively with the Christ Trust and the GC LLC, the “Reporting Persons”).

The 4,481,778 shares of Class B Common Stock held in the aggregate by the Christ Trust, which upon conversion would constitute approximately 7.0% of the shares of Class A Common Stock deemed to be outstanding as of September 30, 2024, may be deemed to be beneficially owned indirectly by Mr. Christ.

The 4,044,004 shares of Class B Common Stock held in the aggregate by the GC LLC, which upon conversion would constitute approximately 6.4% of the shares of Class A Common Stock deemed to be outstanding as of September 30, 2024, may be deemed to be beneficially owned indirectly by Mr. Christ.

Item 2(b).

Address of Principal Business Office or, if None, Residence:

The address for the Reporting Persons is:

c/o Altair Engineering Inc.

1820 E. Big Beaver Road

Troy, MI 48083

Item 2(c).

Citizenship:

Mr. Christ is a citizen of the United States. The Christ Trust is governed by the laws of Arizona. The GC LLC is organized under the laws of Michigan.

Item 2(d).

Title of Class of Securities:

Class A common stock, $0.0001 par value per share (the “Common Stock”)

Item 2(e).

CUSIP No.:

021369103

Item 3.

If This Statement Is Filed Pursuant to Section 240.13d-1(b) or 240.13d-2(b) or (c), check whether the Person Filing is a:

Not Applicable.

Item 4.

Ownership:

As reported in the cover pages to this report, the ownership information with respect to the ownership of the Class A Common Stock of the Company by Mr. Christ as Trustee of the Christ Trust, Manager of the GC LLC, Co-Trustee of the Dana Trust and Co-Trustee of the Lauren Trust is provided as of September 30, 2024:


(a) Amount Beneficially Owned:		9,450,684*

(b) Percent of Class:		13.9%*

(c) Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:		9,450,684*

(ii) Shared power to vote or to direct the vote		0

(iii) Sole power to dispose or to direct the disposition of:		9,450,684*

(iv) Shared power to dispose or to direct the disposition of		0

As reported in the cover pages to this report, the ownership information with respect to the ownership of the Class A Common Stock of the Company by the Christ Trust is provided as of September 30, 2024:


(a) Amount Beneficially Owned:		4,481,778*

(b) Percent of Class:		7.0%*

(c) Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:		4,481,778*

(ii) Shared power to vote or to direct the vote		0

(iii) Sole power to dispose or to direct the disposition of:		4,481,778*

(iv) Shared power to dispose or to direct the disposition of		0

As reported in the cover pages to this report, the ownership information with respect to the ownership of the Class A Common Stock of the Company by the GC LLC is provided as of September 30, 2024:


(a) Amount Beneficially Owned:		4,044,004*

(b) Percent of Class:		6.4%*

(c) Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:		4,044,004*

(ii) Shared power to vote or to direct the vote		0

(iii) Sole power to dispose or to direct the disposition of:		4,044,004*

(iv) Shared power to dispose or to direct the disposition of		0

*	This report on Schedule 13G, is being jointly filed by (i) the Christ Trust, (ii) the GC LLC, and (iii) Mr. Christ, as the Trustee of the Christ Trust, the Manager of the GC LLC, the Co-Trustee of the Dana Trust and the Co-Trustee of the Lauren Trust.

Each of the foregoing beneficial ownership percentages is based upon 59,517,279 shares of Class A Common Stock of the Company outstanding as of September 30, 2024, which is based on information provided by the Company to the Reporting Persons.

Item 5.

Ownership of Five Percent or Less of a Class

Not Applicable.

Item 6.

Ownership of More Than Five Percent on Behalf of Another Person

Not Applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person

Not Applicable.

Item 8.

Identification and Classification of Members of the Group

Not Applicable.

Item 9.

Notice of Dissolution of Group

Not Applicable.

Item 10.

Certification

Not Applicable.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: November 8, 2024

GEORGE J. CHRIST

/s/ Raoul Maitra

Name: Raoul Maitra

Title: Attorney-in-fact for

George J. Christ **

CHRIST REVOCABLE TRUST DATED MAY 8, 2015

/s/ Raoul Maitra

Name: Raoul Maitra

Title: Attorney-in-fact for Christ Revocable Trust dated May 8, 2015 **

GC INVESTMENTS, LLC

/s/ Raoul Maitra

Name: Raoul Maitra

Title: Attorney-in-fact for GC Investments, LLC**

**	A power of attorney was previously filed with the Commission and is incorporated herein by reference to Exhibits 99.2, 99.3 and 99.4 to the Schedule 13G filed by George J. Christ on February 14, 2018.

The original statement shall be signed by each person on whose behalf the statement is filed or his authorized representative. If the statement is signed on behalf of a person by his authorized representative other than an executive officer or general partner of the filing person, evidence of the representative’s authority to sign on behalf of such person shall be filed with the statement: Provided, however, That a power of attorney for this purpose which is already on file with the Commission may be incorporated by reference. The name and any title of each person who signs the statement shall be typed or printed beneath his signature.

Attention: Intentional misstatements or omissions of fact constitute Federal criminal violations (See 18 U.S.C. 1001).

Exhibit Index


Exhibit No.		Exhibit

99.1		A Joint Filing Agreement was previously filed with the Commission and is incorporated herein by reference to Exhibit 99.1 to the Schedule 13G/A filed by George J. Christ on February 14, 2019.

Names of Reporting Persons

George J. Christ

Check the Appropriate Box if a Member of a Group

(a) ☐ (b) ☐

SEC Use Only

Citizenship or Place of Organization

United States

Altair Engineering Inc. SC 13G/A