I left my iPad on a plane, how can i attempt to locate it?

If you have not enabled Find My iPad, you can't track, lock or wipe your iPad

The only way to find a lost iOS device is to use the Find my iPhone app or www.icloud.com. For this to work, you have to enable this feature on the device prior to loss. If you didn't do this, there is no way to find it. Neither Apple nor your carrier will find it for you.

Setup Find my iPhone:

http://support.apple.com/kb/PH2697

Here's a good tip from Kappy on what to do if you device is lost or stolen:

https://discussions.apple.com/docs/DOC-3362

Call the airline. Maybe someone turned it in to lost and found.

Apple (and no one else) can not assist (with serial number or iCloud) in finding a lost or stolen iPad.

Report to police along with serial number. Change all your passwords.

These links may be helpful.

How to Track and Report Stolen iPad

http://www.ipadastic.com/tutorials/how-to-track-and-report-stolen-ipad

Reporting a lost or stolen Apple product

http://support.apple.com/kb/ht2526

iCloud: Locate your device on a map

http://support.apple.com/kb/PH2698

Report Stolen iPad Tips and iPad Theft Prevention

http://www.stolen-property.com/report-stolen-ipad.php

How to recover a lost or stolen iPad

http://ipadhelp.com/ipad-help/how-to-recover-a-lost-or-stolen-ipad/

iCloud: Locate your device on a map

http://support.apple.com/kb/PH2698

How to Find a Stolen iPad

http://www.ehow.com/how_7586429_stolen-ipad.html

Apple Product Lost or Stolen

http://sites.google.com/site/appleclubfhs/support/advice-and-articles/lost-or-st olen

Oops! iForgot My New iPad On the Plane; Now What?

http://online.wsj.com/article/SB10001424052702303459004577362194012634000.html

If you don't know your lost/stolen iPad's serial number, use the instructions below. The S/N is also on the iPad's box.

How to Find Your iPad Serial Number

http://www.ipadastic.com/tutorials/how-to-find-your-ipad-serial-number

iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number

http://support.apple.com/kb/HT4061

 Cheers, Tom 😉