Does the iPhone Air have eSIM? Yes

Yes, the iPhone Air supports eSIM, so it can take a travel eSIM as long as it is carrier unlocked.

What to know about the iPhone Air

There is no SIM tray in any country, including mainland China: it uses eSIM only.

It takes an eSIM, so you can buy a data plan now and install it before you fly. Pick your destination.

Two minutes on the phone itself settles it, whichever version you have.

Dial *#06#
Open the phone app and dial *#06#. If a number labelled EID appears, your phone supports eSIM.
On an iPhone
Go to Settings, then Cellular (or Mobile Data). If you see Add eSIM or Add Cellular Plan, it supports eSIM.
Check it is unlocked
A phone bought from a carrier on contract may be locked to it. Ask your carrier, or look for a Carrier Lock line in your settings that says No SIM restrictions.

Set it up before you fly and keep your usual number for calls and texts.

The 30-second check for any phone: the EID, and whether it is unlocked.