Air Transport Services Group Inc. (ATSG): Red Mountain Capital Agrees to Sell 3.8 Million Shares Back to Company

Page 8 of 10

Page 8 of 10 – SEC Filing

CUSIP No. 00922R105 SCHEDULE 13D/A PAGE 8 OF 10 PAGES

Each of RMCP LLC, RMP and RMCP GP affirms membership in a group with each other but
disclaims membership in a group with RMCM or Mr. Mesdag. Each of RMCM and Mr. Mesdag disclaims membership in a group with any person.

The filing of this Schedule 13D shall not be construed as an admission that any Reporting Person is the beneficial owner of any of the shares
of Common Stock that such Reporting Person may be deemed to beneficially own. Without limiting the foregoing sentence, each of RMCM and Mr. Mesdag disclaims beneficial ownership of all shares of Common Stock reported in this Schedule 13D. In
addition, the filing of this Schedule 13D shall not be construed as an admission that any partner, member, director, officer or affiliate of any Reporting Person is the beneficial owner of any of the shares of Common Stock that such partner, member,
director, officer or affiliate may be deemed to beneficially own. Without limiting the foregoing sentence, Mr. Teets disclaims beneficial ownership of all shares of Common Stock reported in this Schedule 13D.

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO SECURITIES OF THE ISSUER

Item 6 of this Schedule 13D is hereby amended to include the following information:

On June 21, 2016, RMP entered into a securities purchase agreement with ATSG (the Securities Purchase Agreement), pursuant to
which RMP agreed to sell, and ATSG agreed to repurchase, 3,825,554 shares of Common Stock for an aggregate purchase price of $50,000,000. The consummation of the transactions contemplated by the Securities Purchase Agreement is expected to occur on
July 5, 2016, except to the extent otherwise provided in the Securities Purchase Agreement.

The foregoing references to and
description of the Securities Purchase Agreement do not purport to be complete and are subject, and are qualified in their entirety by reference, to the full text of the Securities Purchase Agreement, which is incorporated by reference in this
Item 6.

ITEM 7. MATERIALS TO BE FILED AS EXHIBITS.

Item 7 of this Schedule 13D is hereby amended to include the
following information:

Exhibit No.

Description of Exhibit

8 Securities Purchase Agreement, dated as of June 21, 2016, by and between Air Transport Services Group, Inc. and Red Mountain Partners, L.P. (filed herewith).

Follow Air Transport Services Group Inc. (NASDAQ:ATSG)

Page 8 of 10