NEW YORK--(BUSINESS WIRE)--Halper Sadeh LLC, an investor rights law firm, is investigating whether the sale of Air Transport Services Group, Inc. (NASDAQ: ATSG) to Stonepeak for $22.50 per share in cash is fair to Air Transport shareholders. Halper Sadeh encourages Air Transport shareholders to click here to learn more about their legal rights and options or contact Daniel Sadeh or Zachary Halper at (212) 763-0060 or sadeh@halpersadeh.com or zhalper@halpersadeh.com. The investigation concerns w