ATI officer plans 16,500-share sale under Rule 144

ATI INC (ATI) discloses that company officer Timothy J. Harris has filed a notice under Rule 144 for the potential sale of 16,500 shares of ATI common stock through Fidelity Brokerage Services LLC.

Rhea-AI Filing Summary

ATI INC (ATI) discloses that company officer Timothy J. Harris has filed a notice under Rule 144 for the potential sale of 16,500 shares of ATI common stock through Fidelity Brokerage Services LLC. The shares derive from restricted stock vesting awards granted between February 2021 and January 2024. The notice also lists three prior sales over the past three months, each for 16,500 shares of ATI common stock.

Key Figures

Shares subject to Rule 144 notice: 16,500 shares Aggregate market value of shares in notice: $3,185,490.00 Shares outstanding: 136,170,383 shares +3 more

6 metrics

Shares subject to Rule 144 notice 16,500 shares ATI common stock covered in the current Rule 144 filing

Aggregate market value of shares in notice $3,185,490.00 Value associated with 16,500 ATI common shares in the Rule 144 notice

Shares outstanding 136,170,383 shares ATI common shares outstanding as of September 14, 2026

Sale on August 24, 2026 16,500 shares for $3,414,180.00 ATI common stock sold by Timothy J. Harris during past three months

Sale on August 31, 2026 16,500 shares for $3,465,165.00 ATI common stock sold by Timothy J. Harris during past three months

Sale on September 8, 2026 16,500 shares for $3,424,410.00 ATI common stock sold by Timothy J. Harris during past three months

Key Terms

Rule 144, Restricted Stock Vesting, attorney-in-fact

3 terms

Rule 144 regulatory

"See the definition of "person" in paragraph (a) of Rule 144."

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

Restricted Stock Vesting financial

"Common | 02/24/2021 | Restricted Stock Vesting | Issuer"

Restricted stock vesting is the timetable and conditions under which shares granted to employees or insiders become fully owned and can be sold, typically requiring continued work or meeting performance goals. It matters to investors because large blocks of shares can become tradable at once, which can change share supply and price, and because vesting aligns insiders’ incentives with the company’s long‑term performance—think of it like a timed unlock that both rewards and locks in key people.

attorney-in-fact regulatory

"as attorney-in-fact for Timothy Harris"

An attorney-in-fact is the person or entity given legal authority through a power of attorney to act on behalf of another for specific tasks, such as signing documents, voting shares, or handling transactions. For investors, this matters because it lets a trusted representative make timely decisions or complete paperwork when the owner cannot, much like handing keys to someone to run errands on your behalf—so checks on scope and limits of that authority are important.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does ATI (ATI) disclose in this Form 144 filing?

The filing states that Timothy J. Harris, an officer of ATI INC, filed a Rule 144 notice for the potential sale of 16,500 shares of ATI common stock through Fidelity Brokerage Services LLC, with the shares coming from prior restricted stock vesting awards.

How many ATI (ATI) shares are covered by the new Rule 144 notice?

The notice covers up to 16,500 shares of ATI INC common stock, with an indicated aggregate market value of $3,185,490.00 and referencing 136,170,383 shares outstanding as of September 14, 2026.

What is the origin of the ATI (ATI) shares to be sold by Timothy J. Harris?

The filing lists the 16,500 shares as coming from restricted stock vesting awards granted on February 24, 2021, February 27, 2021, February 24, 2022, and January 9, 2024, all described as compensation from the issuer.

What ATI (ATI) stock sales has Timothy J. Harris reported in the past three months?

The document lists three sales of ATI common stock by Timothy J. Harris: 16,500 shares for $3,414,180.00 on August 24, 2026; 16,500 shares for $3,465,165.00 on August 31, 2026; and 16,500 shares for $3,424,410.00 on September 8, 2026.

Which broker is involved in the ATI (ATI) Form 144 sale for Timothy J. Harris?

The filing identifies Fidelity Brokerage Services LLC, located in Smithfield, Rhode Island, as the broker for the potential sale of the 16,500 ATI common shares under the Rule 144 notice.

Who signed the ATI (ATI) Form 144 on behalf of Timothy J. Harris?

The notice is signed “/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Timothy Harris”, dated September 14, 2026.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/14/2026 - 11:58 AM Accepted by SEC EDGAR 09/14/2026 - 11:57 AM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001776844
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	ATI INC
SEC File Number	001-12001
Address of Issuer	2021 MCKINNEY AVENUE DALLAS TEXAS 75201
Phone	4123942800
Name of Person for Whose Account the Securities are To Be Sold	Harris Timothy J
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917	16500	3185490.00	136170383	09/14/2026	NYSE

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	02/24/2021	Restricted Stock Vesting	Issuer			2252	02/24/2021	Compensation
Common	02/27/2021	Restricted Stock Vesting	Issuer			1371	02/27/2021	Compensation
Common	02/24/2022	Restricted Stock Vesting	Issuer			4613	02/24/2022	Compensation
Common	01/09/2024	Restricted Stock Vesting	Issuer			8264	01/09/2024	Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Timothy J. Harris 2021 McKinney Avenue Dallas TX 75201	Common	08/24/2026	16500	3414180.00
Timothy J. Harris 2021 McKinney Avenue Dallas TX 75201	Common	08/31/2026	16500	3465165.00
Timothy J. Harris 2021 McKinney Avenue Dallas TX 75201	Common	09/08/2026	16500	3424410.00

144: Remarks and Signature

Remarks
Date of Notice	09/14/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	05/21/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Timothy Harris
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)