INNOVATIVE SOLUTIONS & SUPPORT INC

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:

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Preliminary Proxy Statement

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Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material under §240.14a-12

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(Name of Registrant as Specified In Its Charter)​

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

Payment of Filing Fee (Check the appropriate box):

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No fee required.

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Fee paid previously with preliminary materials.

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Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a6(i)(1) and 0-11.

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NOTICE OF ANNUAL MEETING OF

SHAREHOLDERS

Dear Shareholder:

You are invited to attend the Annual Meeting of Shareholders of Innovative Solutions and Support, Inc. (the “Company”).

Date: April 16, 2026

Time: 10:00 a.m., Eastern Daylight Time

Location: 720 Pennsylvania Drive, Exton, PA 19341-1129 USA

Purposes of the Meeting:

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To elect seven directors to hold office until the annual meeting of shareholders in 2027, or until their respective successors have been duly elected and qualified;

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To ratify the appointment of Grant Thornton LLP as the Company’s independent registered public accounting firm for the fiscal year ending September 30, 2026;

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To hold a non-binding advisory vote on the frequency of the say-on-pay vote with respect to compensation of the Company’s named executive officers;

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To hold a non-binding advisory vote on named executive officer compensation as disclosed in the Proxy Statement; and

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To transact any other business that may properly come before the meeting.

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Record Date:

January 26, 2026, is the record date for the meeting. This means that holders of the Company’s common stock at the close of business on that date are entitled to receive notice of the meeting and vote at the meeting and any adjournment or postponement of the meeting.

In the event that the meeting is adjourned for one or more periods totaling at least 15 days due to the fact that there is not a proper quorum, the shareholders entitled to vote who attend the adjourned meeting, even if there is not a proper quorum, shall constitute a quorum for the purpose of acting upon any of the named matters above.

The Company considers your vote important and encourages you to vote as soon as possible.