Best answer: The new 2019 iPad Air (3rd generation) has the same dimensions as the 2017 iPad Pro (10.5-inch,) with a slight variation. Though many 10.5-inch iPad Pro cases will fit, no iPad or iPad Air cases will.
- Amazon: Apple Smart Cover ($49)
The new 2019 iPad Air (3rd generation) similar but not the exact same size as the 2017 iPad Pro (10.5-inch)
If you have a Smart Cover from the 10.5-inch iPad Pro released in 2017, you will be able to use it with the new iPad Air (3rd generation.) Or, if you have a sleeve-type case that is designed to fit any sort of tablet, you should be fine. If you have any other iPad case, including an older iPad Air case, it will not fit the new iPad Air.
Unless you’re upgrading specifically from the 2017 iPad Pro (10.5-inch) to the 2019 iPad Air (3rd generation), you’ll be in the market for a new case. The good news is that you don’t have to wait for new cases to come out. Most 10.5-inch iPad Pro cases will fit the 10.5-inch iPad Air just fine.
Keep in mind, however, that the 10.5-inch iPad Pro has four speakers (two on each side), while the iPad Air has two. So any cases made specifically for the 10.5-inch iPad Pro might have an unnecessary second cutout or grill for speakers. Plus, the 10.5-inch iPad Pro has True Tone Flash, while the iPad Air does not. So, any camera holes are going to be bigger than they need to be.
Since the Apple Smart Cover only covers the screen, not the back of the iPad, the slight differences in the camera and speakers won’t matter. Apple notes on their site that the Smart Cover for the new iPad Air (3rd generation) is also compatible with the iPad Pro (10.5-inch.)
Apple Smart Cover
One Smart Cover, two iPads
Apple’s Smart Cover keeps your screen protected when not in use. Embedded magnets activate the sleep/wake functionality. The cover folds back so you can use your iPad at two angles: high up for video watching and lower for typing. This model fits both the old iPad Pro (10.5-inch) and the new iPad Air (3rd generation.)
Source of the article – iMore