I was on Southwest 944 LAS-MHT on 7/1/09 and wondering if there is a easy way to find out the tail # of the aircraft. I usually record the info for the flights I take. However the gates this aircraft was parked at in LAS & MHT the number was blocked by jetways and other aircraft or unreadable due to the viewing angle.
Thanks
Chris 
You could always ask a FA if they’re not busy. And… Damn! That’s a long SWA flight. 
On Southwest’s aircraft, the tail number is on the right as soon as you enter the door. Am trying to locate a picture showing this.
On all airliners, the actual registration certificate is also located above the entry door and/or on the cockpit door.
Can’t find a picture online. I do have a picture of the “Spirit of Kitty Hawk” medallions on the bulkhead but unfortunately it doesn’t show the registration (it’s just outside of the picture).
The “Spirit of Kitty Hawk” is a Boeing 737-3H4 c/n 22941 with the tail number N301SW.
Hope this helps.
-Chris