Left my macbook on a plane and I need the serial number -

PS:

If your MacBook/Air has 'Find My' or 'Find My Mac' turned on ahead of loss;

that could (have been) helpful to identify yours. ~ With just yours identified by

you, in proximity; that is one way to tell. And nobody at Apple could tell yours

from any others. Those records are private, like any other; unknown to Apple.

• Use the Find My app to locate a lost or stolen device - Apple Support

https://support.apple.com/en-us/HT210515

"Learn the different ways you can use the Find My app to

help find your missing device, even if it's gone offline."

"..sign in to iCloud.com/find to locate your device using a browser.."

{For many more details read the support article.}

These Apple support communities are mostly individuals like you; who in their

spare time, help; & are not compensated for their efforts ~ without inside info.

Take care & safe travels!🌞🐝

..note in 'blue links' above..

covers other areas not in other links

+helpful if you're locating MB/Air with iPhone

• Locate a device in Find My iPhone on iCloud.com - Apple Support

https://support.apple.com/en-euro/guide/icloud/mmfc0f2442/icloud

Earlier reply covers most angles with additional links to more.

If your MacBook/Air has been set ahead of time, that's a key.

Good luck & happy computing!🐠😻

Any documentation from when the MacBook was purchased

or serviced, where the SN may have been recorded, or used?

Authorized resellers may have records; not usually, though.

Buyer names and serial numbers aren't often used that way.

Old original boxes and papers, sometimes can be found years

later; for this information sake, if nothing else. An unlikely fate

would be to have anyone find the MacBook, then somehow

have them locate you.

Even 'Find My Mac' could have trouble. That'd be stretch of luck.

Take care & happy trails!🌻🐝

Re: “... where can I get the serial number ...”

If the MacBook was registered to your iCloud account, the serial number will be reflected on https://appleid.apple.com/