Delta Air Lines quietly changed its pet policies last month. Effective March 1, the airline no longer accepts animals in the cargo hold beneath the main cabin, where temperatures can undergo dramatic swings, which can be dangerous to pets. That means pet owners will have to bring their pets in an approved carrier into the main cabin.

Each plane has its own dimensions and approved weight for pet carriers, but the general rule is no pets more than 20 pounds are allowed in the cabin.

In 2015, Delta reported 18 animal-related incidents, and sadly, most of them were deaths and severe injuries. That’s more than American Airlines’ seven incidents, but less than United Airlines’ 23, according to the Department of Transportation’s Air Travel Consumer Report.

This may not have a huge effect on travelers going on vacation, though it could make it very difficult to relocate by plane with your pet, especially if other airlines adopt the practice.