The tragic crash of a UPS flight in Louisville could affect millions of people this holiday season. Travelers won’t be affected, but your holiday packages may be.

Shortly after the MD-11 crashed on Nov. 4, FedEx and UPS voluntarily grounded their fleets of MD-11s, and that move was followed by the FAA issuing an Emergency Airworthiness Directive grounding the aircraft over U.S. skies.

The MD-11 hasn’t flown passengers since 2014, but they still make up a significant portion of cargo transport. According to retired pilot and YouTube airline analyst Captain Steeeve, UPS has 27 MD-11s, comprising 9% of their fleet while FedEx has 25 which makes up about 7%.

Losing that much space could create a cargo crunch between now and the new year.

Airlines will generally buy space on commercial carriers like Delta or United to pick up the slack. However much of that space is already reserved in anticipation of the traditional December uptick.

As a result, people are urged to ship their gifts and packages as early as possible.

Cause For Concern

Three people on the plane and eight people on the ground died when the plane crashed during takeoff. An engine detached from the wing about forty feet off the ground. The plane clipped a structure and crashed into several buildings including a petroleum recycling facility, triggering a second explosion.

A similar incident happened in 1979 and it’s that history that led the FAA to issue the incredibly rare Emergency Airworthiness Directive.