Amazon's fleet of jets is getting bigger.

The online shopping giant said Tuesday that it will lease 15 more Boeing 737s as it seeks to grow its delivery business and get packages to shoppers' doorsteps faster. Amazon is in the midst of speeding up its delivery time to one-day from two for its Prime members.

Amazon said it currently has 42 planes in its fleet and will have 70 by 2021.

The Seattle-based company wants more control over how its packages are delivered and rely less on UPS, the U.S. Postal Service and other carriers. Besides its fleet of planes, Amazon is building several package-sorting hubs at airports and has launched a program that lets contractors start businesses delivering packages in vans stamped with the Amazon logo.

Earlier this month, FedEx (FDX) said it would stop air shipments for Amazon in the United States, reducing its ties with the company to focus on other e-commerce sites.

Amazon (AMZN) said its fleet of planes flies within the U.S.