(WKBN) – The United States Postal service is implementing a new service plan on May 1. The changes could speed up some mail deliveries and slow down others, such as first-class packages.

The transportation workflow changes are meant to move a larger volume of mail at one time but could slow down the process.

The changes will allow for more transport time for long-distance packages but increase volume to be transported by surface transportation, which is more economical and reliable than air transportation, according to the agency.

Sixty-four percent of first-class package service will be unaffected by the changes, 4% will be upgraded from 3-day to 2-day service, and 32% will increase by one or two days.

Packages traveling the greatest distances will be most affected.

The changes are part of a 10-year plan to reverse a projected $160 billion in losses over the next 10 years.