Per the Seattle Times, Amazon is looking to lease more than just trailers:

Amazon.com is negotiating to lease 20 Boeing 767 jets for its own air delivery service, cargo industry executives have told The Seattle Times.

Leasing 20 jets would be a significant expansion of an Amazon trial operation out of Wilmington, Ohio, according to sources. A cargo industry source said Amazon expects to make a decision to go beyond the trial run and pull the trigger on a larger air cargo operation by the end of January.

The cost of the operation wouldn’t be cheap either. Leasing newly built Boeing 767F jets runs to $600,000 to $650,000 a month, according to cargo industry experts. With so few of those jets available, Amazon would likely turn to lease partners to pick up used converted freighter jets. Those cost about $300,000 to $325,000 per month to lease.

Can't stop, won't stop.