Image source: Boeing.

What: Shares of Air Transport Services Group (NASDAQ:ATSG) jumped 26.6% Wednesday after online retailer Amazon.com (NASDAQ:AMZN) agreed to lease planes and was given the option to purchase a stake in the company.

So what: Amazon will be leasing 20 Boeing 767 freighters from Air Transport Services Group for a period of five years with an option for another two years. Amazon was also given warrants to acquire up to 19.9% of Air Transport Services Group's common shares for $9.73 per share. 

This is a big addition to Air Transport Services Group's externally leased fleet, which stood at 30 aircraft at the end of the year.

Now what: While this is a big win for Air Transport Services Group, Amazon may have taken most of the potential upside for investors with its warrants. We also don't know anything about rates Amazon will pay or how much profit this could add to the company's income statement. While investors should look at this signing as a positive, I think the pop today is overdone and investors need to wait and see how Amazon impacts Air Transport Services Group's financials before piling into the stock.