The iPhone 17 Pro and iPhone 17 Pro Max launched in the United States are equipped with an antenna window on the top of the device to allow mmWave 5G signals to pass smoothly. The standard version of the iPhone 17 is not equipped with this antenna window, and the iPhone Air does not support mmWave 5G, so this design is also not available on the device.
From iPhone 12 to iPhone 15, the "antenna window" is standard and made of glass. However, the antenna window was canceled for the first time on the iPhone 16 series, because a "camera control button" was added where the antenna was originally located.
The iPhone 17 Pro series uses a new aluminum unibody design, but radio signals cannot penetrate metal. Therefore, the reintroduced antenna window (which will most likely still be made of glass or the stronger Ceramic Shield ceramic glass) allows mmWave 5G signals to better penetrate the body frame and enable cellular network connections.
No iPhone outside the US supports mmWave 5G, so there is no antenna window on all models sold in other countries.
mmWave is the general name for a group of 5G frequency bands, which focuses on achieving ultra-high-speed transmission over short distances and is suitable for urban environments with dense signals. In contrast, Sub-6GHz 5G signals, although slower, have longer transmission distances and are more suitable for suburban and rural areas.